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PLANT  HABITS  AND  HABITATS  IN  THE  ARID 
PORTIONS  OF  SOUTH  AUSTRALIA 


BY 
WILLIAM  AUSTIN  CANNON 


Published  by  the  Carnegie  Institution  of  Washington 
Washington,  1921 


€^^ 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
Publication  No.  308 


PRESS  OF  GIBSON  BROTHERS,  INC. 
WASHINGTON,  D.  C. 


a.Stait        '^r^ 


CONTENTS. 


PAGE 

List  of  Illustrations v 

Introduction 1 

Phyf  ical  environment  of  the  vegetation  of  Australia 5 

General  physiographical  conditions 5 

Features  of  the  climate  of  Austraha 8 

Rainfall 8 

Evaporation 14 

Relative  humidity 15 

Light 16 

Temperature 18 

Winds 20 

Subterranean  environment 20 

Temperature,  moisture,  and  aeration  conditions  of  the  soil 23 

Aeration  of  the  soil 24 

Temperature  of  the  soil 25 

Certain  characteristics  of  the  vegetation  of  dry  regions 31 

Physical  environment  of  the  vegetation  of  South  Austraha 35 

Physical  geography 35 

Chmate 42 

Temperature 42 

Rainfall 44 

Effective  rainfall 47 

Vegetation  and  plant  habitats  in  vicinity  of  Oodnadatta 50 

Physiography 50 

Climate 55 

Rainfall 55 

Temperature 56 

General  features  of  the  flora  of  South  Austraha 57 

The  northern  portion  of  South  Australia 57 

Vegetation  of  the  Lake  Eyre  basin 58 

Vegetation  at  Oodnadatta 58 

Vegetation  of  the  plains 59 

Vegetation  of  and  about  the  sandhills 60 

The  Copley  environment 64 

Physiography 64 

Chmate. . . . ." 66 

Rainfall 66 

Temperature 67 

Vegetation  of  the  Copley  region. 67 

Vegetation  of  the  "alkali"  plains 68 

Root-habits  of  plants  of  the  plains 70 

Vegetation  of  the  low  hills  and  slopes 73 

Mono-specific  communities 74 

Isolated  species  and  mixed  communities 76 

Vegetation  of  the  washes 77 

Parasitic  phanerogams 79 

Root-habits  of  plants  of  the  washes 80 

Leaf -form  and  leaf-sizes 80 

Vegetation  of  southwestern  South  Austraha 81 

Vegetation  and  environment  at  Ooldea 81 

Physiography 81 

CUmate .* 83 

Habitats 84 

Vegetation  of  the  NuUarbor  Plain 85 

Vegetation  about  Ooldea 86 

Transition  from  the  sandhills  to  the  Nullarbor  Plain 89 

Leaf-form  and  leaf-size 89 

III 


IV  CONTENTS. 

Vegetation  of  southwestern  South  Austraha — Continued.  page. 

Vegetation  and  environment  at  Tarcoola 89 

Physiography 89 

Rainfall  and  temperature 90 

Vegetation 91 

Vegetation  and  environment  at  Port  Augusta 93 

Physiography 93 

Rainfall. . . . ." 94 

Temperature 94 

Vegetation 94 

Sizes  and  forms  of  leaves  and  phyllodia 96 

Vegetation  and  environment  at  Quorn 96 

Climate 99 

Vegetation  and  habitat 100 

Vegetation  of  the  valleys  and  of  Willochra  Plain 101 

Vegetation  of  low  hills 105 

Vegetation  of  the  washes 107 

Root-characters 107 

Mallee  and  the  mallee  regions 108 

Physical  and  climatic  features 109 

Rainfall  and  temperature 109 

Vegetation 110 

Morphological  aspects  of  the  xerophytic  flora  of  South  Austraha Ill 

Leaf-size  and  leaf-form Ill 

Features  of  the  roots  of  South  Australian  plants 114 

Notes  on  some  structural  features  of  perennials 117 

The  phyllodia  in  some  species  of  Acacia 117 

A.  aneura  and  A.  Unophylla 118 

Acacia  continua 120 

Acacia  tarculiensis 122 

Acacia  tetragonophylla 123 

Notes  on  certain  other  species  of  the  region 124 

Bossia'a  walkeii 124 

Casuarina  stricta 124 

Dodona^a  attenuata  and  D.  lobulata 125 

Some  morphological  features  of  the  genus  Eremophila 126 

Fusanus  acuminatus 129 

Gravillea  stenobotrya 130 

Hakea  multilincata  and  H.  leucoptera 130 

Melaleuca  parviflora 131 

Pittosporum  phillyricoides 131 

Triodia  irritans 132 

Certain  reactions  and  adjustments  of  the  plants  of  the  more  arid  portions  of  South 

Australia 133 

Reactions  to  light 133 

Reactions  to  temperature 134 

Reactions  to  a  small  water-supply 134 

Reactions  to  the  subterranean  environment 136 

Bibliography 138 


ILLUSTRATIONS. 

PLATES. 

1,  A.  View  looking  north  from  O'Halloran's  Mount,  Oodnadatta,  showing  lower  plain 

with  upper  plain  at  the  extreme  right  in  background. 
B.  Lower  plain  near  Oodnadatta,  showing  "gibbers"  on  the  surface  and  typical  de- 
pression with  species  of  Eremophila. 

2,  A.  Eremophila  freelingii  in  a  shallow  wash  on  the  slope  of  upper  plain  near  Oodnadatta. 
B.  Eremophila  freelingii  in  a  shallow  wash  on  the  edge  of  upper  plain  west  of  Neales 

River,  Oodnadatta. 

3,  A.  Acacia  cambadgei  in  a  shallow  wash  on  the  slope  connecting  upper  and  lower  plains 

west  of  Neales  River,  Oodnadatta. 
B.  Shoot-tips  with  leaves,  Eremophila  freelingii,  from  upper  plain  west  of  Neales  River, 

Oodnadatta. 
c.  Shoot-tips  with  leaves,  Eremophila  latrobei,  from  a  wash  connecting  upper  and  lower 

plains  west  of  Neales  River,  Oodnadatta. 

4,  A.  Acacia  tetragonophylla,  near  west  base  of  sandhills  east  of  Oodnadatta. 
B.  Acacia  linophylla  on  sandhills  east  of  Oodnadatta. 

c.  Short  channel,  Neales  River,  with  Eucalyptus  rostrata  and  Acacia  stenophylla,  small 
shrubs,  on  the  banks,  Oodnadatta. 

5,  A.  Phyllodia  of  Acacia  linophylla  from  sandhills  near  Oodnadatta. 
B.  Eremophila  neglecla  near  base  of  sandhills  east  of  Oodnadatta. 
c.  Neales  River  bottoms  from  the  lower  plain,  Oodnadatta. 

6,  A.  Shoot-tips  and  phyllodia  of  Acacia  tetragonophylla,  left,  and  A.  cambadgei,  right, 

from  Neales  River,  Oodnadatta. 
B.  Leaves  and  phyllodia  of  Acacia  stenophylla  from  Neales  River,  Oodnadatta. 

7,  A.  Prominent  development  of  horizontal  roots  in  Acacia  cambadgei,  Neales  River, 

Oodnadatta. 

B.  Vegetative  reproduction  in  Acacia  stenophylla  from  floodplain,  Neales  River,  Oodna- 
datta. 

c.  Kochia  sedifolia  on  low  slope  above  Copley  Plain  on  Yudnamutana  road,  Copley. 

8,  A.  Zygophyllum  fruticosum  at  edge  of  Copley  Plain  by  Table  Mountain.     The  trees  in 

the  background  are  Casuarina  lepidophloia ,  Copley. 

B.  Nitraria  schoeberi  hillock  colonies  on  Copley  Plain.  Table  Mountain  is  in  the  back- 
ground at  left,  Copley. 

c.  Detail  of  edge  of  colony  of  Nitraria  schoeberi,  showing  horizontal  prostrate  branches 
by  which  the  hillock  colony  is  extended,  Copley. 

9,  A.  Shoot-tip  of  Eremophila  freelingii  from  low  hills  on  Mount  Series  road,  Copley. 

B.  Eremophila  oppositifolia,  showing  leaves  and  flowers,  from  rounded  low  hills  on 

Mount  Series  road,  Copley, 
c.  Pholidia  scoparia,  "broom, "  from  low  hills  on  Mount  Series  road  east  of  Copley. 

10,  A.  Cassia  sturtii,  constituting  a  mono-specific  community  on  Mount  Series  road,  Copley. 
B.  Mono-specific  community  of  Eremophila  freelingii,  in  low  hills  along  Mount  Series 

road,  Copley, 
c.  Mono-specific  community  of  Pholidia  scoparia  in  low  hills  on  Mount  Series  road, 
Copley. 

11,  A.  Hakea  leucoptera  on  southern  slope  of  Table  Mountain,  Copley. 

B.  Casuarina  lepidophloia,  or  "oak,"  at  south  base  of  Table  Mountain,  Copley, 
c.  Community  of  Zygophyllum  fruticosum  near  Mount  of  Light,  Copley. 

12,  A.  Petalostylis  labicheoides  from  south  base  of  Table  Mountain,  Copley. 
B.  Casuarina  lepidophloia,  Copley. 

c.  Petalostylis  labicheoides  at  south  base  of  Table  Mountain,  Copley. 

D.  Shoot  habit  of  Hakea  leucoptera,  with  fruit,  from  Table  Mountain,  Copley . 

13,  A.  Melaleuca  glomerata,  the  "white"  tea-tree,  in  a  small  branch  of  Leigh's  Creek,  Mount 

Series  road,  Copley. 
B.  Melaleuca  parviflora,  the  "black"  tea-tree,  near  Myrtle  Springs  road,  Copley, 
c.  Eucalyptus  rostrata,  the  red  gum,  on  Leigh's  Creek,  Copley. 

14,  A.  Eremophila  alternifolia  at  side  of  small  wash  near  Mount  of  Light,  Copley. 
B.  Eremophila  longifolia  on  edge  of  Copley  Plain  near  Leigh's  Creek,  Copley. 


VI  ILLUSTRATIONS. 

15,  A.  Shoot-tip  showing  leaves  and  fruits  of  Melaleuca  parviflora,  or  "black"  tea-tree,  from 

Myrtle  Springs  road,  Copley. 
B.  Tip  of  shoot  of  Eremophila  alternifoUa  with  flowers  and  leaves,  Copley. 
c.  Leafy  shoot  of  Acacia  varians  from  a  wash  east  of  Copley. 
D.  Melaleuca  glomerata,  "white"  tea-tree,  from  Leigh's  Creek,  Copley. 

16,  A.  Eremophila  longifolia,  Copley. 

B.  Branch  of  Acacia  tetragonophylla  with  short  spinose  phyllodia  and  inflorescence 

buds,  Copley. 
c.  Acacia  tetragonophylla  in  low  hills  on  Mount  Series  road,  east  of  Copley. 

17,  A.  Leafy  shoot-tips  with  fruit  of  Fusanus  spicatus,  the  "quandang,"  and  F.  acuminatus, 

the  native  "peach,"  Mount  Deception  Range,  Copley. 
B.  Myoporum  platycarpum  from  low  hills  in  Mount  Series  road,  Copley. 
c.  Shoot-tip  with  leaves  and  fruit  of  Loranthxis  exocarpi  and  leafy  branch  of  host, 

Acacia  sentis,  Copley. 
D.  Loranthus  exocarpi,  at  right,  and  Eremophila  brownii,  host,  Copley. 

18,  A.  Loranthtis  quandang,  with  oval  leaves,  and  the  narrow-leaved  form  of  Acacia  aneura, 

the  "mulga,"  its  host.     From  Mount  Searles  road,  east  of  Copley. 

B.  Loranthus  linearifolius  on  Acacia  tetragonophylla.  The  host  is  shown  with  character- 
istic spine-like  phyllodia.     Copley. 

c.  Loranthus  exocarpi,  with  leaves  and  fruit  and  shoot-tip  of  its  host,  Myoporum  platy- 
carpum, Copley. 

19,  A.  Acacia  aneura,  the  mulga,  at  Ooldea. 

B.  Eucalyptus  oleosa  by  a  wash  at  the  eastern  base  of  Mount  Deception  Range.  The 
prominent  stem  base  and  enlarged  crown  of  the  taproot,  both  characteristics 
of  the  "mallee,"  are  shown.     Copley. 

20,  A.  Detail  of  branch  of  Acacia  colletioides  showing  spine-like  phyllodia  Ooldea. 

B.  Narrow  "leaf"  form  of  Acacia  aneura,  the  mulga,  at  Ooldea.     Young  fruits  are  shown 

on  one  of  the  branches. 
c.  Broad  "leaf"  form  of  Acacia  aneura,  the  mulga,  at  Ooldea. 

21,  A.  Eucalyptus  pyriformis  a,t  Ooldea.     Various  species  of  .Acacia  and  the  mallee,  E^ucaiyp- 

tus  incrassata  var.  dumosa,  make  up  the  surrounding  woody  vegetation.     The 
floor  is  bare. 
B.  Eucalyptus  leucoxylon  var.  macrocarpa,  middle  ground,  and  E.  incrassata  var.  dumosa, 
on  the  hillside  beyond,  near  Ooldea. 

22,  A.  Fruits  of  Eucalyptus  pyriformis  from  Ooldea.     The  fruits  are  about  5  cm.  in  diameter. 
B.  Leptospermum  loevigatum  var.  minus,  in  flower,  from  the  Ooldea  Soak. 

c.  The  shrubby  Eucalyptus  leucoxylon  var.  macrocarpa  in  flower,  from  Station  408  near 
Ooldea. 

23,  A.  Pholidia  santalina  from  mallee  community  of  low  ridge  west  of  Quorn. 
B.  Callistemon  teretifolius,  from  ridge  on  Mount  Arden  road,  Quorn. 

c.  Aphyllous  Acacia  continua  from  low  hills  on  the  Pichi  Richi  road,  west  of  Quorn. 
D.  Tip  of  branch  of  Acacia  calamifolia,  in  fruit,  showing  the  linear  phyllodia.     From 
open  Casuarina  forest  on  the  Melrose  road,  east  of  Quorn. 

24,  A.  Gravillea  stenobotrya  shoot  showing  leaves  and  fruits,  from  Station  408,  near  Ooldea. 
B.  Leaf  habit  of  Eremophila  rotundifolia,  Tarcoola. 

c.  Tips  of  a  branch  of  Acacia  rigens,  with  phyllodia,  Tarcoola. 

D.  A  fruiting  branch  of  Acacia  tarculiensis  showing  characteristic  phyllodia.  From 
type  habitat,  Tarcoola. 

25,  A.  Acacia  rigens,  the  "myall,"  with  various  halophytes,  on  plain  north  of  Tarcoola. 

B.  Thicket  of  mallee.  Eucalyptus  oleosa,  on  sloping  saltbush  plain,  foothills  of   the 

Flinders,  east  of  Port  Augusta,  near  Saltia. 
c.  "Beef  wood,"  Gravillea  stenobotrya,  on  the  crest  of  eandhill  by  Station  408,  near 

Ooldea. 

26,  A.  Forest  of  Eucalyptus  rostrata  on  Saltia  creek,  east  of  Port  Augusta. 
B.  Pine  community,  Callitris  robusta,  at  Warren's  Gorge,  near  Quorn. 

c.  View  in  mallee  scrub,  about  2  miles  north  of  Quorn.  Eucalyptus  odorala  and  E. 
oleosa  in  the  background.     Bunches  of  Triodia  irritans  in  the  foreground. 


ILLUSTRATIONS.  VII 

27,  A.  Branches  of  Acacia  sublanata,  showing  small  and  rigid  phyllodia,  Quorn. 

B.  Eutaxia  empetrifolia,  showing  the  small  flowers  and  linear  short  leaves,  Quorn. 
c.  Branches  of  Acacia  pycnanlha,  the  "golden  wattle,"  showing  the  character  of  the 
large  phyllodia,  Quorn. 

28,  A.  View  about  2  miles  west  of  Quorn,  taken  from  a  grassy  ridge  and  looking  upon  a  ridge 

which  is  covered  with  mallee.     In  the  intervening  valley  are  a  few  specimens 

of  Eucalyptus  leucoxylon  var.  pauperita. 
B.  Hakea  leucoptera  on  the  edge  of  the  mallee  scrub,  about  2  miles  north  of  Quorn. 

Small  shoots  which  spring  from  superficial  roots  of  the  larger  plants  are  in  the 

foreground. 
c.  Western  slope  of  ridge  along  Mount  Arden  road,  Quorn,  with  Triodia  irritans  and 

Trichinium,  dominant  grasses.     Dead  fruiting  stalks  of  Xanthorrhcea  semi- 

plana  shown  in  the  foreground;  mallee,  Eucalyptus  sp.,  in  the  background. 

29,  A.  Bossicea  walkeri  on  summit  of  a  sandhill  by  Station  408,  near  Ooldea. 

B.  Hakea  multilineata  on  the  crest  of  a  sandhill  by  Station  408,  near  Ooldea,  with  Euca- 
lyptus incrassata  var.  dumosa,  a  mallee,  in  the  fiats  below.  Bunches  of 
spinifex,  Triodia  irritans,  are  to  be  seen  between  the  mallee. 

c.  Branch  with  withered  flower-spike  and  leaves  of  Hakea  multilineata,  from  Station 
408,  near  Ooldea. 

D.  Melaleuca  uncivaia  in  fruit,  from  the  sandhills  by  Station  408,  near  Ooldea. 

30,  A.  A  community  of  Acacia  pycnanlha,  the  golden  wattle,  by  a  streamway  on  the  Mount 

Brown  road,  Quorn. 
B.  A  large  specimen  of  Eucalyptus  leucoxylon  var.  pauperita,  by  a  wash  on  the  Mount 

Arden  road,  Quorn.     A  comparison  with  the  automobile  will  give  an  idea  of 

its  size. 
c.  Vegetative  reproduction  in  Hakea  leucoptera.     A  young  shoot,  removed  from  the 

soil,  is  shown  taking  its  origin  from  a  horizontal  root.     Quorn. 

31,  A.  Exposure  of  roots  of  mallee.  Eucalyptus  sp.,  by  a  narrow  wash,  showing  the  abun- 

dance of  superficial  roots.     Along  the  Mount  Arden  road,  Quorn. 
B.  Root  exposure  of  Eucalyptus  leucoxylon  var.  pauperita  by  erosion  of  the  bank  of 
stream  above  Warren's  Gorge.     The  roots  were  washed  out  for  a  distance 
exceeding  16  meters.     Quorn. 

32,  A.  Scattered  groups  of  Melaleuca  parviflora,  in  the  mallee  scrub  near  Blanchtown. 

B.  Flood  plain  of  the  Murray  River  showing  open  forest  of  Eucalyptus  rostrata  partly 

submerged,  Blanchtown. 
c.  View  in  mallee.  Eucalyptus  sp.,  scrub  on  Murray  flats  near  Blanchtown. 

FIGURES. 

1.  Physical  divisions  of  Austraha,  after  Gregory,  1916,  to  which  has  been  added  the 

10-inch  isohyet.     The  shaded  areas  have  an  altitude  of  1,000  feet  or  more 
above  the  sea. 

2.  Mean  annual  rainfall  map  of  Austraha,  adapted  from  Hunt. 

3a.  Duration  of  wet  seasons,  after  Taylor,  1916.  "The  periods  shown  on  the  map  include 
those  months  in  which  the  average  rainfall  exceeds  the  geometric  mean  of  the 
monthly  rainfalls." 

3b.  Wettest  months  of  the  year,  after  Hunt's  meteorological  map  of  Austraha,  1916. 

4a.  Mean  rainfall  of  Australia  for  January,  after  Hunt. 

4b.  Mean  rainfall  of  Australia  for  April,  after  Hunt. 

5a.  Mean  rainfall  of  Austraha  for  July,  after  Hunt. 

5b.  Mean  rainfall  of  Austraha  for  October,  after  Hunt. 

6.  Graphs,  after  Hunt,  showing  average  monthly  rainfall  and  mean  monthly  evaporation, 
in  inches,  for  various  places  in  Austraha. 

7a.  Mean  humditiy  of  Australia  for  January,  after  Taylor,  1918. 

7b.  Mean  humidity  of  Austraha  for  July,  after  Taylor,  1918. 

8a.  Mean  annual  evaporation  in  Australia,  after  Hunt. 

8b.  Average  yearly  temperature  of  Austraha,  after  Hunt. 

9a.  Mean  temperature  of  Australia  for  January,  after  Hunt. 

9b.  Mean  temperature  of  Austraha  for  July,  after  Hunt. 


VIII  ILLUSTRATIONS. 

10.  Chief  physical  divisions  and  geographical  plan  of  South  Australia,  after  Howchin  and 

Gregory,  with  the  5-,  10-,  and  15-inch  isohyets. 

11.  Graphs  shomng  the  annual  (total)  and  "non-effective"  rainfall  for  1901-1906  at 

Oodnadatta  (a),  Copley  (6),  and  Quorn  (c).  South  Australia,  based  on  records 
suppUed  by  the  Adelaide  office  of  the  Commonwealth  Bureau  of  Meteorology. 

12.  Acacia  linophylla,  transverse  section  of  phyllode,  semi-diagrammatic,   X  72.     The 

large  proportion  of  mechanical  tissue  is  indicated  (sc),  and  the  protected 
position  of  the  chlorenchyma  (ch).  The  relatively  heavy  covering  of  hairs 
is  indicated  by  the  stippling. 

13.  Same.     Detail  of  margin  of  phyllode  to  show  the  nature  of  the  sclerenchyma  and 

epidermal  cells  and  the  presence  of  glandular  trichomes,  X  700. 

14.  Same.     Detail  of  inner  portion  of  chlorenchyma  showing  its  relation  to  the  fibro- 

vascular  bundle  at  the  left,  X  700. 

15.  Acacia  continua,  transverse  section  of  chlorophyll-bearing  stem,  X  52.5. 

16.  Acacia  telragonophylla,  cross-section  of  phyllode,  semi-diagrammatic,  X  85. 

17.  Casuarina  stricta,  transverse  section,  semi-diagrammatic,  of  chlorophyll-bearing  stem, 

X  72.  The  chlorenchyma  is  shown  partly  protected  by  the  heavy  epidermis 
and  partly  by  the  furrows  with  the  trichomes,  of  which  the  latter  are  not 
shown.  The  enlarged  outer  ends  of  the  sclerenchyma  also  act  in  the  same 
capacity. 

18.  Eremophila  allernifolia,  detail  of  young  stem  with  glandular  trichome,  X  52.5. 

19.  Same.     Transverse  section  of  leaf  showing  old  glandular  trichome,  heavy  epidermis, 

and  its  covering  of  a  resinous  substance. 

20.  Eremophila  freelingii,  semi-diagrammatic  transverse  section  of  leaf  to  show  the  size 

and  frequency  of  internal  glands  (gl),  X  52.5. 

21.  Eremophila  rotundifolia,  longitudinal  section,  semi-diagrammatic,  X  52.5,  to  show  the 

relatively  large  internal  glands  and  the  very  heavy  covering  of  hairs  {tr). 

22.  Fusanus  acuminatixs,  fragment  of  leaf  showing  chlorenchyma  and  a  group  of  tracheids, 

X  350. 

23.  Same.     Cross-section  of  leaf  to  show  the  heavy  epidermis  consisting  of  two  layers  of 

cells,  X  350. 

24.  Gravillea  stenobotrya,  semi-diagrammatic  transverse  section  of  leaf.     The  various 

tissues  are  as  indicated.  Trichomes  and  stomata  are  confined  to  the  ventral 
side,  X  52.5. 

25.  Same.     Detail  of  leaf,  dorsal  side,  in  cross-section,  to  show  the  greatly  elongated 

epidermal  cells  and  well-marked  palisades,  X  350. 

26.  Hakea  leucoptera,  leaf  fragment,  in  transverse  section,  with  very  heavy  epidermis  and 

deeply  sunken  stoma  and  papillate  processes  in  stomatal  canal.  The  presence 
of  sclerenchymatous  fibers  in  the  paUsade  chlorenchyma  is  shown.     X  350. 

27.  Hakea  muUilineata,  semi-diagrammatic  cross-section  of  leaf.     The  prominent  devel- 

opment of  mechanical  tissue  and  dorsi ventral  nature  of  the  leaf  structure  are 
indicated.     X  52.5. 

28.  Same.     Fragment  of  leaf,  cross-section,  to  show  heavy  epidermis,  deeply  sunken 

stoma,  and  pronounced  paUsade  character  of  the  chlorenchyma,  X  350. 

29.  Pittosporum  phyllyrwoides,  fragment  of  dorsal  side  of  leaf,  transverse  section,  to  show 

the  2-  or  3-layered  epidermis,  X  350. 

30.  Same,  ventral  side  of  leaf.     The  heavy  outer  epidermal  wall,  the  single  cell  layer  of 

the  epidermis,  and  the  superficially  placed  stoma  are  indicated.     X  350. 

31.  Triodia  irritans,  transverse  section  of  leaf,  semi-diagrammatic,  showing  its  infolded 

condition  and  the  position  and  relative  abundance  of  the  main  tissues,  X  85. 
In  figures  12  to  31  the  tissues  are  designated  as  follows:  ch,  chlorenchyma; /a;,  conductive 
tissue;  gl,  internal  gland;  hd,  hypoderm;  sc,  sclerenchyma;  ep,  epidermis; 
fu,  fibro-vascular  tissue. 


PLANT  HABITS  AND  HABITATS  IN  THE  AEID 
POETIONS  OF  SOUTH  AUSTEALIA. 


INTRODUCTION. 

Australia,  especially  South  Australia,  holds  much  of  interest  to  the 
student  of  the  vegetation  of  arid  regions.  Where  rain  is  abundant 
plants  compete  with  one  another  in  a  very  real  way  for  room  in  which 
to  live  and  for  sunhght  by  which  they  gain  energy  for  various  life 
processes,  but  in  regions  of  scanty  rainfall,  as  in  portions  of  South 
Australia,  there  is  abundance  of  room  and  of  Ught.  Here  the  "struggle" 
is  associated  with  the  water  relation ;  it  is  that  of  the  individual  plant 
with  an  arid  environment,  and  not  individual  with  individual.  When 
viewed  from  this  standpoint  the  island  continent  is  seen  to  be  the  field 
of  a  vast  botanical  experiment  in  which  may  be  observed  the  reaction 
of  numerous  species  and  innumerable  individuals  to  a  physical  en- 
vironment, a  leading  characteristic  of  which  is  a  relatively  small  water- 
supply.  Moreover,  owing  to  the  great  age  of  Australia,  it  is  possible 
that  nowhere  else  have  plants  been  exposed  to  and  influenced  by  an 
arid  environment  for  a  longer  period  of  time. 

The  physical  background  of  the  Austrahan  plants  is  in  a  measure 
unique.  The  dry  region  is  very  extensive.  Some  idea  of  its  size  can 
be  had  by  the  statement  that  it  has  nearly  as  great  an  area  as  all  Arabia, 
and  as  a  matter  of  fact  is  larger  than  all  other  regions  of  the  kind  south 
of  the  equator.  Living  and  developing  under  an  environment  of  which 
the  keynote  is  aridity,  the  flora  of  the  continent  as  a  whole  bears  a 
xerophytic  stamp  and  appears  to  possess  a  degree  of  uniformity  which 
constitutes  one  of  its  most  marked  characteristics.  Wherever  one 
goes  in  Australia,  he  encounters  trees  and  shrubs  with  leathery,  ever- 
green leaves.  In  the  better-watered  portions  the  trees  are  large  and 
numerous  and  there  is  an  extensive  transpiration  surface,  but  in 
portions  less  favored  in  this  particular  the  trees  are  not  large,  a  shrubby 
type  of  vegetation  prevails,  and  the  transpiration  siu-face  is  also  much 
restricted  in  area.  Between  the  two  extremes  there  are  innumerable 
intermediate  conditions  in  which  the  gradations  are  quantitative 
rather  than  qualitative.  When  studied  in  some  detail,  however,  there 
may  be  found  a  bewildering  variety  of  adjustments  to  the  environment, 
often  monotonous  perhaps  in  outward  appearance,  and  which  have  in 
a  measure  the  force  of  belying  the  generahzation  just  made. 

The  physical  and  biological  complexes  which  enter  into  our  concep- 
tion of  what  constitutes  an  arid,  more  especiafly  a  desert,  region  are 
made  up  of  many  features.  It  is  true  that  they  center  around  the 
important  factor  of  a  small  water-supply,  but  they  all  should  be 
logically  included  in  any  definition  of  such  regions  with  scanty  rainfall. 


2  PLANT   HABITS   AND   HABITATS   IN   THE 

Owing,  however,  in  part  to  the  difficulty  in  evaluating  the  biological 
value  of  the  accessory  factors,  such  as  light  intensity,  relative  humidity 
of  the  air,  rate  of  evaporation,  and  temperature  of  the  air,  and  in  part 
to  the  fact  that  such  secondary  factors  may  change  in  relative  force 
with  changes  in  the  amount  of  the  rainfall,  it  is  difficult  to  express 
adequately  what  constitutes  a  ''desert,"  or  even  the  degree  of  aridity. 
Nevertheless  it  is  important  to  have  some  method  of  comparison. 
Thus,  the  extremes  in  amount  of  rainfall  have  been  used  (MacDougal, 
1914: 175),  and  the  amount  of  evaporation  for  any  given  year  has  been 
compared  with  the  precipitation  for  the  same  year,  and,  finally,  com- 
parisons have  been  instituted  between  the  moisture  content  of  the  soil 
and  the  rate  of  evaporation  of  the  air  (Shreve,  1915:92). 

The  intensity  of  the  aridity  has  also  been  expressed  biologically  in 
terms  of  the  relative  number  of  annuals  in  a  region  (Paulsen,  1912 :  159). 
It  was  not  convenient  in  the  present  instance  to  use  these  methods,  but 
it  appeared  necessary  nevertheless  (mainly  for  convenience  in  reference) 
to  have  some  ready  means  of  comparing  one  region  studied  with 
another,  and  in  the  end  the  device  was  resorted  to  of  using  the  rainfall 
only.  An  arbitrary  classification  of  regions  based  on  the  amount  of 
rain  was  consequently  adopted,  which  is  as  follows:  A  region  having  5 
inches,  or  less,  of  rain  annually  is  a  desert;  one  with  a  rainfall  between  5 
and  10  inches  is  arid;  and  a  region  in  which  the  amount  of  rain  is  be- 
tween 10  and  15  inches  is  semi-arid.  In  all  cases,  therefore,  in  which 
reference  is  made  in  the  text  to  regions  so  designated  the  appropriate 
rainfall  will  at  once  be  understood. 

The  study  of  plants  in  the  field  may  be  said  to  proceed  mainly  along 
three  lines,  which,  although  more  or  less  intermingled,  are  fundamentally 
quite  different.  Thus,  the  leading  emphasis  can  be  placed  on  the 
plants  as  species,  and  their  occurrence  (local  as  well  as  general)  can 
merely  be  catalogued;  this  is  plant  geography  in  a  narrow  sense.  Or, 
the  mutual  relationships  of  plants  can  be  investigated ;  this  is  one  formal 
branch  of  plant  ecology.  Or,  finally,  the  investigation  can  take  into 
consideration  mainly  the  relations  of  plants  to  the  physical  environ- 
ment in  which  they  are  placed;  this  third  phase  of  the  general  subject 
is  intimately  related  to  experimental  researches  along  lines  suggested  by 
field  observations  and  is  not  to  be  dissociated  from  laboratory  studies; 
this  can  be  referred  to  as  physiological  plant  ecology.  It  is  the  last 
type  of  ecological  research  which  the  writer  has  had  especially  in  mind 
when  making  field  studies,  and  though  it  has  not  been  practicable  to 
carry  out  direct  experiments  on  subjects  suggested  by  the  observations, 
it  has  been  of  interest  and  profit  to  interpret  the  observations  so  far  as 
possible  in  the  light  of  experimental  results  abeady  accomphshed  on 
analogous  lines  and  with  analogous  plants  by  various  researchers. 

In  addition  to  viewing  the  living  plants  from  a  physiological  stand- 
point, another  point  of  view  has  been  of  use,  the  comparative.  In  all 
instances  the  plants  observed  have  been  studied  in  the  light  of  the 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA.  6 

writer's  previous  experiences  in  the  dry  portions  of  North  America,  in 
southern  Algeria,  and  in  portions  of  Egypt,  and  these  experiences 
have  been  of  incalculable  assistance  in  attempts  at  interpreting  the 
various  features  of  Austrahan  plant  hfe  observed. 

It  is  impossible  adequately  to  acknowledge  the  very  many  kind- 
nesses shown  the  writer  while  in  Australia.  A  friendly  and  helpful 
spirit  of  assistance  and  cooperation  was  shown  by  a  large  number  and 
on  very  many  occasions;  but  especial  acknowledgment  must  be  given 
Professor  and  Mrs.  T.  G.  B.  Osborn,  of  the  University  of  Adelaide,  who 
helped  greatjy  to  make  the  visit  pleasant  as  well  as  profitable.  Dr. 
and  Mrs.  R.  S.  Rogers,  of  Adelaide,  well  known  for  their  studies  on 
the  Orchidacese,  acted  as  guides  on  several  botanical  excursions  into  the 
Mount  Lofty  Ranges,  and  in  other  ways  were  helpful.  J.  M.  Black 
esq.,  of  Adelaide,  an  authority  on  South  Australian  plants,  very 
kindly  determined  those  plants  which  were  collected  by  the  writer. 
Among  them  Mr.  Black  found  some  new  stations  and  a  species  of 
Kochia  collected  at  Copley  which  was  previously  undescribed.  Men- 
tion should  also  be  made  of  the  assistance  of  Alfred  Cocks  esq.,  of 
Adelaide,  the  former  proprietor  of  "Wilgena"  station,  near  which 
Tarcoola  is  situated,  whose  acquaintance  with  the  ''back  blocks"  of 
the  state  is  very  extensive.  Thomas  Gill  esq.,  of  Adelaide,  was  of  as- 
sistance in  procuring  for  the  writer  useful  works  on  Australian  explora- 
tion and  in  other  ways;  C.  S.  Owen-Smith  esq.,  of  Adelaide,  was  also 
helpful  in  various  ways;  and  finally,  not  to  mention  others,  G.  A. 
Hobler  esq.,  and  Capt.  E.  W.  Saunders,  of  the  Commonwealth  rail- 
ways, kindly  placed  conveniences  at  the  writer's  disposal  at  Ooldea, 
and  were  of  much  assistance  in  other  ways  and  at  other  times. 

Especial  acknowledgment  must  be  made  of  permission  to  use  figures, 
tables,  or  data  for  the  presentation  of  many  characteristics  of  the 
physical  environment  of  the  South  Australian  plants.  Figure  1  is 
from  Australia,  1916,  by  Professor  J.  W.  Gregory;  figure  10  is  an 
adaptation  of  a  figure  in  the  Geography  of  South  Australia,  1909,  by 
Howchin  and  Gregory.  Those  noted  as  being  from  Hunt  are  by  H.  A. 
Hunt  esq.,  Commonwealth  meteorologist,  and  have  been  taken  from 
various  publications  of  the  Commonwealth  Bureau  of  Meteorology. 
The  figures  from  Taylor  are  by  Dr.  Griffith  Taylor,  physiographer, 
Commonwealth  Meteorological  Office,  and  are  in  part  from  publications 
of  the  bureau  and  in  part  from  other  publications  as  noted.  As  a 
whole  the  figures  were  prepared  to  serve  other  than  botanical  ends 
and  in  most  of  them  some  changes  have  been  made,  inconsiderable  in 
certain  instances,  to  suit  the  needs  of  the  present  study.  Figure  11 
is  based  on  data  supplied  by  the  Adelaide  office  of  the  Commonwealth 
Bureau  of  Meteorology.  In  the  main  the  climatological  data  were 
supplied  by  the  Commonwealth  Bureau  or  were  derived  from  its  pub- 
lications, and  in  either  case  acknowledgment  is  made  explicitly  in  the 
course  of  the  study. 


PLANT   HABITS   AND    HABITATS  IN    THE 


The  follownng  species,  determined  by  J.  M.  Black  esq.,  were  collected 
at  Oodnadatta,  Copley,  Quorn,  Port  Augusta,  Tarcoola,  and  Blanch- 
town,  and  in  the  regions  contiguous  to  these  places : 

Eutaxia  empetrifolia  Schlecht. 
Exocarpus  aphylla  R.  Br. 
spartea  R.  Br. 
Fusanus  acuminatus  R.  Br. 

spicatus  R.  Br. 
Geigera  parviflora  Lindl. 
Glycine  dandestina  Wendl. 
Gravillea  stenobotrya  F.  v.  M. 
Hakea  leucoptera  R.  Br. 

multilineata  Meiss. 
Helichrysum  spiculatum  D.  C. 
Heterodendrum  olaeefolium  Desf . 
Indigofera  australis  Wild.  var.  minor  Benth. 
Jasminum  lineare  R.  Br. 
Kochia  cannoni  J.  M.  Black  (n.  s.) 
decaptera  F.  v.  M. 
eriantha  F.  v.  M. 
planifolia  F.  v.  M. 
pyrmidata  Benth. 
sedifolia  F.  v.  M. 
villosa  Lindl. 
Leptospermum  Isevigatum  F.  v.   M.   var. 

minus. 
Loranthus  exocarpi  Behr. 

linearifolius  Hook, 
pendulus  Sieb. 
quandang  Lindl. 
Melaleuca  glomerata  F.  v.  M. 

parviflora  Lindl. 
Menkea  australis  Lehm. 
Myoporum  platycarpum  R.  Br. 
Nicotiana  suaveolens  Lehm. 
Nitraria  schoeberi  L. 
Olearia  muelleri  Benth. 

pimeleoides  Benth. 
pannosa  Hook. 
Pholidia  santahna  F.  v.  M. 

scoparia  R.  Br. 
Pimelea  microcephala  R.  Br. 
Pittosporum  phillyrasoides  D.  C. 
Rhagodia  parabolica  R.  Br. 
Saliccrnia  tenuis  Benth.  (n.  s.?). 
SciBvola  collaris  F.  v.  M. 
Senecio  anethifolius  A.  Cunn. 
gregorii  F.  v.  M. 
magnificus  F.  v.  m. 
Si  da  corrugata  Lindl. 
Solanum  ellipticum  R.  Br. 
Templetonia  aculeata  Benth. 

egena  Sweet. 
Trichinium  incanum  R.  Br. 

spathulacum  R.  Br. 
Triodia  irritans  R.  Br. 
Zygophyllum  billardieri  D.  C. 

crenatum  F.  v.  M. 
fruticulosum  D.  C. 
prismatothecum  F.  v.  M. 


Acacia  aneura  F.  v.  M. 

brachystachya  Benth. 
calamifoha  Sweet, 
cambadgei  R.  T.  Bake. 
coUetioides  A.  Cunn. 
continua  Benth. 
hakeoides  A.  Cunn. 
iteaphylla  F.  v.  M. 
kempeana  F.  v.  M. 
linophylla  W.  V.  Fitz. 
oswaldi  F.  V.  M. 
pycnantha  Benth. 
randelliana  W.  V.  Fitz. 
rigens  A.  Cunn. 
.    salicina  Lindl. 
sentis  F.  v.  M. 
stenophylla  A.  Cimn. 
sublimata  Benth. 
tarculiensis  J.  M.  Black, 
varians  Benth. 
Atriplex  mumularium  Lindl. 
quinii  F.  v.  M. 
spongiosum  F.  v.  M. 
vesicarium  Hew. 
Bassia  echinopsilla  F.  v.  M. 
lanicuspis  F.  v.  M. 
paradoxa  F.  v.  M. 
Bossiaea  walkeri  F.  v.  M. 
Bursaria  spinosa  Cavan. 
Calandrinia  pusilla  Lindl. 
CaUistemon  teretifolius  F.  v.  M. 
Callitris  robusta  R.  Br. 
Cassia  artemioides  Gaud, 
brownii  R.  Br. 
eremophila  A.  Cunn. 
sturtii  R.  Br. 
Cassinia  aculeata  (Lab.)  R.  Br. 
Casuarina  lepidophloia  F.  v.  M. 

stricta  Ait. 
Cheilanthes  tenuifolia  Schwartz. 
Dodonsea  attenuata  A.  Cunn. 

bursarifoHa  Behr  et  F.  v.  M. 
lobulata  F.  v.  M. 
Enchylaena  toqientosa  R.  Br. 
Eremophila  alternifoha  R.  Br. 
brownii  F.  v.  M. 
'*'     freehngii  F.  v.  M. 
latrobei  F.  v.  M. 
longifolia  F.  v.  M. 
neglecta  J.  M.  Black, 
oppositifolia  R.  Br. 
paisleyi  F.  v.  M. 
rotundifolia  F.  v.  M. 
Eucalyptus  incrassata  Lebill.  var.  dumosa 
Maiden, 
odorata  F.  v.  M. 
oleosa  F.  v.  M. 
rostrata  F.  v.  M. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  0 

PHYSICAL  ENVIRONMENT  OF  THE  VEGETATION  OF 
AUSTRALIA. 

The  vegetational  environment  of  Australia,  including  the  more 
arid  portions,  has  a  complex  geographical  background.  The  island 
continent  is  separated  biologically,  as  well  as  physically,  from  other 
continents  and  has  been  so  separated  for  an  immense  period  of  time. 
Long  geological  ages  also  have  passed  since  a  large  portion  of  the 
surface  was  covered  by  the  sea.  The  physiography  is  relatively 
monotonous,  as  might  be  expected  from  the  fact  that  possibly  the  area 
may  be  regarded  as  a  vast  peneplain.  The  latitudinal  situation  also  is 
of  importance  in  influencing,  really  in  shaping,  the  leading  characteristic 
of  its  climate.  Projecting  as  it  does  far  into  the  interior,  the  state  of 
South  Australia  shares  in  the  general  physical  characteristics  of  the 
continent,  but  it  also  holds  in  certain  regards  a  peculiar  relation  to  the 
sister  states.  Its  southern  shores  are  washed  by  the  cool  seas,  while  the 
northern  boundaries  are  parched  and  baked  under  a  tropic  sun.  It  has 
the  most  typically  continental  climate  of  all  the  states  (Howchin  and 
Gregory,  1909:17).  Such  are  some  of  the  features  which  have  con- 
stituted and  which  now  constitute  the  broad  characters  of  the  physical 
environment  of  the  vegetation  of  Australia,  including  that  of  the 
central  state,  and  under  which  by  physiological  reactions  there  has 
slowly  developed  the  vegetation  familiar  to  us  at  the  present  day. 

GENERAL  PHYSIOGRAPHICAL  CONDITIONS. 
The  general  physiographical  conditions  of  Australia  have  many 
points  of  interest  in  connection  with  the  present  paper.     Gregory 
(1916:25-27)  states  that: 

"Australia  as  a  whole  is  a  great  plateau  land.  It  is  a  fragment  of  a  large 
continent,  the  rest  of  which  has  been  snapped  off  along  great  fractures. 
.  .  .  The  mountain  system  is  not  determined  by  any  dominant  lines  of 
folding  of  the  earth's  crust,  like  those  which  have  formed  the  Alps  and  the 
Himalayas.  Australia  was  folded  at  an  early  period  in  the  earth's  history; 
and  all  its  ancient  fold-mountains  have  long  since  been  worn  down.  The  chief 
existing  features  in  the  relief  of  Australia  are  due  to  vertical  earth-movements, 
by  which  some  parts  of  the  area  have  been  raised  to  high  plateaus  and  others 
have  sagged  downward  into  deep  basins.  The  margins  of  the  plateaus  have 
been  carved  into  valleys.  .  .  .  The  eastern  margin  of  the  old  plateau 
has  been  dissected  by  powerful  streams  into  deep  valleys,  which  are  separated 
by  steep-sided  and  flat-topped  ridges ;  and  in  some  districts  river  erosion  has 
been  so  active  that  very  little  of  the  original  surface  has  been  left.  .  .  . 
Western  Australia,  on  the  other  hand,  owing  to  its  smaller  rainfall  and  feebler 
rivers,  retains  more  of  the  old  plateau  surface.  .  .  .  The  inner  part  of 
the  plateau  is  a  vast  gently  undulating  country,  with  low  rounded  hills,  except 
where  some  hard  wind-etched  boss  of  rock  rises  abruptly  from  the  plains. 
Wide,  shallow  depressions  run  together  like  the  converging  branches  of  a  river; 
and  these  valleys  are  divided  by  the  irregularities  of  their  floors  into  basins, 
which  in  wet  seasons  may  contain  lakes  of  little  depth;  but  usually  they  are 


6 


PLANT  HABITS  AND  HABITATS   IN  THE 


sheets  of  salt-incrusted  clay,  or  damp  mud  and  salt  marsh.  .  .  .  Owing 
to  the  absence  of  recent  fold  mountains  the  rehef  of  the  continent  depends  on 
the  weathering  of  the  old  plateau  and  the  formation  of  highlands  and  low- 
lands by  the  uplift  or  subsidence  of  wide  tracts  of  country." 

The  same  writer  divides  the  continent  of  Australia  into  the  Eastern 
Highlands,  the  Great  Plains,  and  the  Western  Plateau.  The  rela- 
tive extent  and  position  of  each  division  is  indicated  in  figure  1.    It 


Fig.  1. — Physical  divisions  of  Australia,  after  Gregory,  ]916,  to  which  has  been  added  the  10-inch 
isohyet.     The  shaded  areas  have  an  altitude  of  1,000  feet  or  more  above  the  sea. 

will  be  seen  that  the  desert-arid  regions  lie  in  the  western  and  cen- 
tral divisions  and  that  possibly  half  of  the  area  within  the  10-inch 
isohyet  has  an  altitude  of  1,000  feet  or  more.  On  the  other  hand,  a  not 
inconsiderable  proportion  of  the  whole  of  the  desert-arid  regions  is 
situated  in  the  artesian  basin  of  the  Great  Plains  regions  and  is  below 
the  level  of  the  sea. 

The  Western  Plateau  is  not  level,  but  several  mountain  chains  rise 
upon  it;  certain  of  these  attain  to  considerable  altitude,  as,  for  example, 
Mount  Woodrofe,  of  the  Musgrave  Range,  which  is  over  5,000  feet 
above  the  sea,  approximately  3,000  feet  higher  than  the  surrounding 
plain  (Jack,  1915). 


ARID   PORTIONS  OF   SOUTH   AUSTRALIA.  7 

To  quote  Jutson  (1914:20),  the  interior  of  the  great  plateau  is  arid 
and  has  no  permanent  rivers.  The  drainage  runs  into  shallow  basins 
(with  no  outlet  except  at  times  of  great  flows  of  water),  called  "salt" 
or  ''dry"  lakes.  There  is,  however,  fresh  water  to  be  found  where  the 
catchment  has  been  suitable,  as,  for  example,  the  "soaks"  like  the  well- 
known  one  at  Ooldea,  and  basins  in  the  rocks,  as  vividly  described  by 
Carnegie  (1898:191).  But,  with  the  possible  exception  of  the  former, 
these  have  no  significance  so  far  as  the  vegetation  is  concerned.  As 
the  interior  has  little  rain  and  no  rivers,  there  is  no  water  table.  The 
picture  that  the  great  plateau  presents  as  a  whole  is  therefore  a  very  arid 
one,  both  as  regards  the  aerial  and  the  sub  aerial  plant  environment. 

The  great  plateau  is  regarded  by  Jutson  (1914:20-21)  as  being  an 
old,  uplifted  surface,  a  vast  peneplain,  whose  surface  has  been  much 
destroyed,  planed  down,  and  often  not  recognizable.  In  the  southern 
half  of  Western  Australia  the  rocks  of  a  very  large  area  are  probably 
pre-Cambrian,  while  in  the  southeastern  corner  they  are  Mesozoic  or 
early  Tertiary  (Jutson,  I.  c),  which  is  the  region  known  as  the  Nullarbor 
Plains.  Where  the  great  plateau  of  the  western  part  of  the  continent 
joins  the  big  central  artesian  basin,  the  rocks  are  also  of  the  Mesozoic 
and  more  recent  ages.  As  a  whole,  therefore,  the  great  plateau  is  of 
very  great  geological  antiquity. 

That  portion  of  the  desert-arid  region  which  lies  within  the  Great 
Plains  varies  in  altitude  from  somewhat  below  the  level  of  the  sea  to 
1,000  feet  or  more  above  it.  One  of  the  characteristic  physiographical 
features  is  the  presence  of  steppes  (Spencer  and  Gillen,  1912:5)  or 
table-lands  of  Upper  Cretaceous  and  Lower  Cretaceous  formations 
(Jack,  1915:13),  which  connect  the  Great  Plains  to  the  Western 
Plateau.  On  the  east  the  plains  gradually  rise  to  the  highlands  of 
eastern  Australia.  The  sandhills,  which  are  especially  to  be  found  to 
the  north  and  east  of  Lake  Eyre,  but  occur  to  the  northwest  as  well,  are 
built  of  material  derived  by  erosion  from  the  desert  sandstone  of  the 
steppes,  and  the  "gibber"  plains,  or  stony  deserts,  also  trace  their  origin 
to  these  Cretaceous  plateaus  and  are  the  residue  remaining  in  place. 

A  most  striking  feature  of  the  Great  Plains  regions  is  the  presence 
of  several  large  lakes  which  in  earlier  geological  times  contained  fresh 
water  but  are  now  saline  wastes,  usually  carrying  water  only  after 
heavy  rains.  Of  these.  Lake  Eyre  and  Lake  Eyre  South  are  the  largest, 
covering  an  area  of  5,000  square  miles  when  filled  with  water  (Howchin 
and  Gregory,  1909: 100).  Lake  Eyre  receives  the  discharge  of  several 
rivers  of  intermittent  flow.  At  various  places  in  the  Lake  Eyre  basin 
natural  artesian  wells  are  found  whose  outlets  are  raised  into  small  hills 
through  the  deposition  of  minerals  held  in  solution.  Also,  numerous 
"bores,"  deep  wells,  have  been  sunk  for  economic  purposes.  The  water 
that  supplies  the  wells  of  whatever  sort  is  derived  from  rains  falling 
in  the  Eastern  Highlands  or  is  chiefly  plutonic  (Pittman,  1914). 


PLANT  HABITS   AND   HABITATS   IN   THE 


FEATURES  OF  THE  CLIMATE  OF  AUSTRALIA. 
Rainfall. 

There  are  four  major  rainfall  regions  in  Australia,  according  to  Taylor 
(1918- :  10),  namely,  the  summer-rain  region  of  the  north,  the  winter- 
rain  region  of  the  south,  a  region  of  uniform  rains  in  the  east,  and  a 
region  of  little  rain  in  the  center  and  middle  west.  The  seasonal 
shifting  of  the  climatic  complex  north-south,  following  the  declination 
of  the  sun,  operates  to  bring  about  the  seasonal  rains.  Tropical  storms, 
cyclones,  reach  inland  in  summer  and  cover  the  entire  northern  portion 
of  the  continent.  They  extend  south  barely  as  far  as  Oodnadatta. 
The  winter  storms,  on  the  other  hand,  affect  the  southern  portion  and 
extend  north  only  about  as  far  as  Farina,  South  Australia  (Taylor, 
1918^:  10).  These  accompany  the  northern  extension  of  the  prevailing 
westerlies  which  in  summer  are  far  to  the  south  of  Australia.  There  is, 
therefore,  a  belt  of  territory  running  roughly  east  and  west  which  is 
beyond  the  usual  reach  either  of  the  winter  or  of  the  summer  rains. 
This  dry  central  region  comprises,  according  to  Taylor,  37  per  cent  of 
the  area  of  the  continent. 

Table  1. — Rainfall  at  the  capitals. 


Capital. 

Average 
rainfall, 
in  inches. 

No.  of 
days  rain. 

Percentage 

of  rainfall 

in  6  wettest 

months. 

Adelaide 

20.88 
46.65 
23.39 
25.32 
32.91 
24.49 

123 
130 
144 
133 
115 
159.5 

70 

67.7 

55 

49 

86.9 

59.9 

Brisbane .... 

Hobart 

Perth.. 

The  leading  characteristics  of  the  rainfall  in  the  humid  regions  can  be 
illustrated  by  that  at  the  capitals  of  the  different  states.  These  are 
summarized  in  table  1 .  At  Adelaide  and  at  Perth  rain  occurs  mostly  in 
the  winter  season;  at  Brisbane  it  is  mostly  in  summer;  at  Sydney  it  is 
mostly  in  late  summer,  autumn,  and  early  winter,  while  at  Melbourne 
and  at  Hobart  it  is  fairly  evenly  distributed  throughout  the  year. 

So  far  as  the  well-being  of  the  vegetation  as  a  whole  is  concerned  the 
reliability  of  the  rains  (or  the  want  of  this)  is  of  capital  importance. 
And  in  a  general  way  the  reliability  of  the  rains  decreases  with  the 
decrease  in  the  amount  of  the  rainfall,  which  it  will  be  seen  only  serves 
to  intensify  the  effects  of  progressive  aridity.  Thus  we  find  that  in  the 
dry  interior  of  the  continent  there  is  a  mean  variation  equal  to  40  to  50 
per  cent  from  the  normal  (Taylor,  1918S  fig.  4.)  In  some  years  very 
little  rain  falls  at  any  season,  while  in  others  almost  the  entire  yearly 
rain  may  fall  within  a  few  hours.  While  the  rainfall  throughout  the 
interior  is  as  a  rule  very  unreliable,  the  portion  of  the  dry  mid-region 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA. 


9 


which  has  the  least  reliable  rainfall,  according  to  the  same  author,  is  in 
Western  Australia.  At  Roebum,  for  example,  the  following  extremes 
in  precipitation  have  been  recorded :  In  the  year  1891  the  rainfall  was 
0.13  inch  only;  in  the  year  1900,  at  the  opposite  extreme,  the  rainfall 
amounted  to  42  inches.  The  region  of  greatest  rain  variability  is 
roughly  equal  in  extent  to  that  which  lies  within  the  10-inch  isohyet, 
but  it  is  situated  somewhat  farther  north  and  hence  is  largely  in  the 
region  of  summer  rains. 


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Fi6.  2. — Mean  annual  rainfall  map  of  Australia,  adapted  from  Hunt. 

It  can  be  seen  that  with  the  possible  exceptions  of  the  dry  interior 
on  the  one  hand  and  the  humid  regions  on  the  other,  the  precipitation 
of  the  continent  can  be  characterized  as  periodic.  There  are  thus 
many  days  in  the  year  when  no  rain  falls  and,  as  just  suggested,  these 
may  occur  in  large  degree  consecutively.  The  actual  number  of  rainless 
days  may  be  surprisingly  large,  as  the  following  will  indicate;  the 
figures  are  for  the  year  1912  only:  In  the  humid  regions  the  average 
number  of  days  without  rain  for  26  stations  is  306.2.  In  the  semi-arid 
regions  the  average  of  24  stations  is  332  rainless  days,  the  average  for 
16  stations  in  the  arid  regions  is  328.4,  and  finally,  the  average  number 
of  rainless  days  in  the  desert,  6  stations,  is  346.4.  It  is  possible  that  the 
regular  recurrence  of  rainless  periods  over  most  of  Australia  is  a  very 
important  factor,  although  a  very  complex  one,  in  giving  the  vegetation 
as  a  whole  the  xerophytic  stamp  it  bears. 


10  PLANT   HABITS   AND   HABITATS   IN  THE 

Table  2. — Mean  monthly  and  annual  rainfall  {in  inches).* 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

Oodnadatta: 

Mean   

0.71 

5.18 

0.71 
4.16 

0.57 
4.32 

0.18 
1.79 

0.23 
1.54 

0.64 

2.77 

0.28 
1.68 

0.11 
0.60 

0.32 
2.21 

0.34 
2.03 

0.38 
1.41 

0.38 
1.79 

4.85 
8.92 

Highest 

Lowest 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

1.54 

Leigh's  Creek: 

(Copley)  Mean 

0.67 

0.52 

0.80 

0.54 

1.06 

1.11 

0.50 

0.69 

0.75 

0.47 

0.53 

0.76 

8.40 

Highest 

4.76 

3.05 

4.70 

3.78 

5.84 

4.72 

2.24 

3.02 

3.58 

2.06 

2.36 

3.78 

15.6 

Lowest 

Quorn: 

Mean 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

1.95 

0.64 

0.45 

0.61 

0.96 

1.58 

2.03 

1.57 

1.84 

1.30 

1.32 

0.87 

0.65 

13.8 

Highest 

3.20 

2.53 

3.53 

6.38 

6.86 

4.88 

6.15 

5.53 

4.00 

4.44 

5.36 

2.45 

25.7 

Lowest 

0.0 

0.0 

0.0 

0.0 

0.01 

0.23 

0.14 

0.06 

0.0 

0.09 

0.0 

0.0 

7.43 

Adelaide: 

Mean 

0.72 

0.63 

1.06 

1.85 

2.71 

3.10 

2.65 

2.50 

1.98 

1.72 

1.17 

0.96 

21.0 

Highest 

4.00 

2.67 

4.60 

6.78 

7.75 

8.58 

5.38 

6.24 

4.64 

3.83 

3.55 

3.98 

30.8 

Lowest 

0.0 

0.0 

0.0 

0.06 

0.20 

0.42 

0.36 

0.35 

0.45 

0.17 

0.04 

0.0 

11.3 

Kalgoorlie: 

0.43 
2.50 

0.73 
4.68 

0.90 
5.02 

0.78 
3.43 

1.31 
3.12 

1.27 
3.00 

0.91 
2.08 

0.90 
3.18 

0.52 
3.29 

0.79 
3.14 

0.58 
2.76 

0.62 
2.57 

9.74 
16.4 

Highest 

Lowest 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.22 

0.0 

0.0 

0.0 

0.0 

0.0 

4.75 

*  Supplied  by  the  Commonwealth  Bureau  of  Meteorology,  Central  Bureau,  Melbourne. 

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FiQ.  3a. — Duration  of  wet  seasons,  after  Taylor,  1916.     "The  periods  shown  on  the  map  include 
those  months  in  which  the  average  rainfall  exceeds  the  geometric  mean  of  monthly  rainfalls." 


ARID   PORTIONS   OF    SOUTH   AUSTRALIA. 


11 


FiQ.  36.— Wettest  months  of  year,  after  Hunt's  meteorological  map  of  Australia,  1916. 

y1^4-A^"- 

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Fig.  4o. — Mean  rainfall  of  Australia  for  January,  after  Hunt. 


12 


PLANT   HABITS   AND   HABITATS  IN  THE 


Fio.  ib. — Mean  rainfall  of  Australia  for  April,  after  Hunt. 


Table  3. — Average  yearly  evaporation  and  rainfall  for  representative  Australian  stations 


Station. 

Evaporation, 
inches. 

Rainfall, 
inches. 

Station. 

Evaporation, 
inches. 

Rainfall, 
inches. 

Perth 

66.13 
146.57 
156.02 

87.74 
54.28 
97.10 

33.26 

9.5 

8.27 

9.40 

21.66 

10.99 

Broken  Hill 

Sydney 

Melbourne 

85.63 
36.91 
38.38 
51.95 
32.37 
149.67 

9.66 
48.16 
25.60 
47.05 
25.50 

9.94 

Laverton 

Cue 

Kalgoorlie 

Adelaide 

Hobart 

Wiluna 

Alice  Springs 

ARID  PORTIONS   OF   SOUTH   AUSTRALIA. 


13 


Fio.  5a. — Mean  rainfall  of  Australia  for  July,  after  Hunt. 


Table  4. — Mean  monthly  and  annual  evaporation  (in  inches). 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

Alice  Springs: 

12.2 
15.4 
8.1 

8.9 
11.2 
7.3 

6.8 
7.9 
5.7 

12.4 
15.1 
8.9 

10.5 
13.8 
6.5 

7.3 
9.1 
4.9 

6.0 
7.1 
5.3 

10.2 
14.3 
6.4 

9.5 
12.6 
6.9 

5.7 

7.2 
4.2 

5.4 
6.5 
4.1 

9.0 
11.3 
6.2 

6.8 
8.4 
5.0 

3.3 
4.9 
2.1 

4.0 
4.6 
3.2 

5.8 
9.0 
3.5 

4.8 
5.5 
3.7 

1.9 

2.8 
1.2 

3.1 

3.6 
2.6 

3.7 

4.8 
1.7 

3.3 
4.1 
2.6 

1.2 
1.8 

.8 

2.5 
3.0 
1.9 

2.4 
3.1 
1.6 

3.6 
4.4 
2.3 

1.2 
2.3 

.8 

2.6 
3.2 
2.3 

2.3 
3.0 
1.1 

5.0 
6.4 
3.9 

1.8 
2.7 
1.1 

3.4 
4.1 

2.7 

3.5 
4.3 
2.9 

7.1 
8.5 
5.9 

2.8 
3.8 
2.0 

4.4 
5.5 
3.9 

5.3 
6.9 
3.9 

9.2 
11.7 

5.8 

4.7 
7.3 
3.1 

5.6 
7.1 
4.7 

7.4 
9.5 
4.6 

10.6 
12.8 
8.6 

6.5 

7.8 
4.8 

5.7 
6.7 
5.2 

9.9 
11.6 
6.6 

12.0 
14.1 
8.9 

8.4 
10.4 
6.5 

6.8 
8.3 
6.4 

12.5 
17.8 
9.1 

95.2 
108.4 
84.2 

54.4 
60.9 
46.6 

57.0 
60.9 
52.8 

85.0 
96.6 
71.9 

Highest  mean. . 
Lowest  mean .  . 
Adelaide: 

Highest  mean. . 
Lowest  mean .  . 
Eucla: 

Highest  mean. . 
Lowest  mean .  . 
Coolgardie: 
Mean     

Highest  mean. . 
Lowest  mean .  . 

*  Supplied  by  the  Commonwealth  Bureau  of  Meteorology,  Central  Bureau,  Melbourne. 


14 


PLANT   HABITS   AND   HABITATS   IN   THE 


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Evaporation. 

A  relatively  high  rate  of  evaporation  is  one  of  the  most  striking 
features  of  the  Australian  climate  taken  as  a  whole  (table  4  and  fig.  8a). 
In  a  large  portion  of  the  continent  it  exceeds  the  rainfall,  and  in  certain 
regions,  as  indicated  by  table  3,  the  difference  between  evaporation  and 
rainfall  may  be  very  great.  Moreover,  in  a  fairly  large  area  the  annual 
evaporation  is  relatively  and  actually  high.  Thus  in  about  40  per  cent 
of  the  continent  the  total  evaporation  is  100  inches  or  more  annually. 
Since  there  is  a  direct  relation  between  the  rate  of  evaporation  and  the 
temperature  of  the  air,  as  well  as  with  other  climatic  factors,  such  as 
relative  humidity  and  rainfall,  it  follows  that  there  is  a  regular  course 
run  by  it  during  the  year.  This  feature  is  shown  in  figure  6.  It  will  be 
observed  that  in  regions  of  winter  rainfall  the  course  of  the  monthly 
evaporation  amount  is  fairly  consistently  opposed  to  that  of  the  rain- 
fall, but  that  in  regions  within  the  zone  of  summer  rains,  as  at  Brisbane, 
there  is  more  or  less  coincidence  between  the  course  of  the  two  climatic 
elements.  Table  4  is  a  detailed  summary  of  the  mean  monthly  and 
annual  evaporation  amounts,  as  well  as  the  highest  and  the  lowest 
means,  for  4  stations. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


15 


The  region  having  the  highest  rate  of  evaporation  is  in  the  western 
part  of  the  central  portion  of  the  continent.  At  Cue,  for  example, 
there  is  a  record  of  156.02  inches  in  one  year.  This  amount  far  exceeds 
that  reported  for  Aden,  on  the  Indian  Ocean,  and  Calexico,  Cahfornia 
(MacDougal,  1914:6),  but  is  not  so  great  as  reported  for  Ghardaia, 
Algeria,  which  is  5,309.7  mm.  or  17.5  feet  (Cannon,  1913:9). 


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Fig.  6. — Graphs,  after  Hunt,  showing  average  monthly  rainfall  and  mean  monthly  evaporation, 
in  inches,  for  various  places  in  Australia. 

Relative  Humidity. 
The  relative  humidity  isopleths  when  plotted  on  a  map  of  Australia 
parallel  fairly  closely  the  coast-line  (Taylor,  19182:8).  Hence  they  are 
concentric.  Other  interesting  features  are  the  relatively  large  area 
which  hes  within  the  40  per  cent  relative  humidity  isopleth,  which  is 
approximately  27  per  cent  of  the  continent,  and  the  changes  in  area  of 
the  region  included  within  this  isopleth  with  its  north-south  seasonal 
movement.    These  features  are  illustrated  in  figures  7a  and  76. 


16 


PLANT   HABITS   AND   HABITATS   IN   THE 


The  average  relative  humidity  (3  p.  m.  readings)  for  the  year  1912 
for  arid-subhumid  stations,  compiled  from  Hunt  (1912),  illustrates  the 
wide  distribution  of  the  low  relative  humidities.  The  average  for  13 
arid  stations  gives  a  relative  humidity  of  32.3  per  cent.  The  average  for 
a  like  number  of  semi-arid  stations  is  37  per  cent.  And,  finally,  the 
average  for  9  subhumid  stations  is  42.1  per  cent. 


Fig.  7a. — Mean  humidity  of  Australia  for  January,  after  Taylor,  1918. 

In  summer,  when  the  center  of  minimum  relative  humidity  is 
farthest  south,  practically  all  of  South  Australia  is  included  within  the 
50  per  cent  relative  humidity  isopleth,  and  possibly  in  over  one-half 
of  the  state  at  this  season  the  relative  humidity  averages  40  per  cent 
or  less. 

Light. 

The  amount  and  quality  of  light  to  which  plants  are  exposed,  as  is 
well  known,  are  extremely  variable.  The  light  in  humid  regions,  for 
example,  is  less  intense  and  contains  less  of  the  more  refrangible  rays, 
the  blue,  violet,  and  ultra-violet,  than  that  in  arid  regions.  The  light 
in  high  latitudes  is  weaker  than  that  of  the  tropics.  From  its  geo- 
graphical position,  as  well  as  from  the  fact  that  much  of  the  continent 
ia  relatively  and  actually  arid,  it  follows  that  much  of  Australia  is 
exposed  to  an  intense  light,  rich  in  actinic  or  chemical  rays.     In  the 


ARID    PORTIONS   OF    SOUTH   AUSTRALIA. 


17 


Fig.  lb. — Mean  humidity  of  Australia  for  July,  after  Taylor,  1918. 

absence  of  data  dealing  directly  with  the  subject  we  may  get  some  idea 
of  the  amount  of  light  as  well  as  of  its  variation  in  amount  over  the 
continent  by  comparing  the  number  of  hours  of  sunshine  at  several 
representative  stations  (table  5). 

Table  5. — Hours  of  sunshine  for  representative  stations  in  Australia.     (Hunt,  1912 :  625.) 


Station. 

Total 

sunshine 

for  year  1912, 

in  hours. 

Mean 

daily  amount, 

in  hours. 

Greatest 

daily  amount, 

in  hours. 

Perth 

2,834.3 
2,479.0 
3,350.0 

2,758.8 
1,984.5 

7.7 
6.8 
9.2 
7.7 
5  4 

13.2 
13.9 
12.3 
12.7 
13.5 
12.3 
11.3 
11.8 

Adelaide 

Alice  Springs 

Brisbane 

Sydney 

Canberra   

2,206.9                6.1 
1,862.1     1           5.1 
1,861.6                5.1 

Melbourne 

Hobart 

There  is  an  interesting  relation  between  the  light  and  the  reaction  of 
the  plant  to  other  environmental  factors.  In  regions  having  little 
rainfall  especially,  the  exposed  surface  of  plants  is  reduced  in  extent  so 
that  the  amount  of  water  lost  is  thereby, also  reduced.     This  is  carried 


18  PLANT   HABITS   AND    HABITATS    IN   THE 

to  the  extreme  under  desertic  conditions.  But  the  plant  is  under  the 
necessity  of  manufacturing  food  through  energy,  in  part  derived  from 
Hght.  This  calls  for  a  leaf  expanse  adequate  to  this  end.  Therefore 
forces  are  in  constant  operation  which,  on  the  one  hand,  tend  to  decrease 
the  extent  of  leaf  surfaces,  and  on  the  other  tend  in  the  opposite  direc- 
tion. But  in  the  arid  regions,  as  has  just  been  remarked,  light  is 
abundant  and  of  proper  quality,  so  that  a  relatively  or  actually  small 
expanse  of  leaves,  made  necessary  by  the  high  rate  of  evaporation,  is 
also  sufficient  for  the  manufacture  of  foods. 

According  to  Schimper  (1903:714)  light  in  high  altitudes,  which  may 
have  many  of  the  properties  of  that  of  the  desert,  is  very  intense  and  is 
rich  in  actinic*  rays.  It  operates  to  retard  the  growth  of  shoot  axes  and 
of  foliage.  It  induces  the  construction,  on  the  part  of  the  plant,  of 
certain  pigments  which  may  possibly  act  as  a  screen,  and  at  the  same 
time  it  may  bring  about  the  more  rapid  destruction  of  the  chlorophyll. 
The  development  of  palisade  cells  is  apparently  forwarded  by  such 
conditions  as  obtain  in  the  mountains  and  on  the  desert,  thus  tending  to 
increase  the  xerophytic  character  of  the  vegetation  characteristic  of 
these  regions. 

Temperature. 

Australia  possesses  a  very  equable  climate;  indeed,  according  to 
Hunt  (1914:124),  it  is  the  most  pacific  and  equable  of  all  the  conti- 
nents. This  in  part  is  owing  to  its  insularity,  in  part  to  its  geographical 
position,  and  in  part  to  the  comparatively  low  relief  of  its  surface. 
Taylor  (1918^:4)  makes  an  interesting  comparison  as  to  the  temperature 
on  parallel  degrees  of  latitude  between  Australia  and  the  average  for 
each  hemisphere.  It  appears  that  the  Australian  tropics  are  hotter 
than  the  average  for  either  hemisphere.  On  the  other  hand,  the  tem- 
perate regions  of  Australia  are  somewhat  hotter  than  parallel  latitudes 
in  other  continents  of  the  southern  hemisphere,  but  the  opposite  is  true 
with  regard  to  Australia  and  the  northern  hemisphere.  However,  one 
of  the  hottest  regions  on  the  globe,  according  to  the  same  author,  is  in 
Australia.  He  states  that  only  four  localities  are  known  with  an  aver- 
age annual  temperature  over  84°  F.  Of  these,  Timbuctu  has  an  average 
temperature  of  84°;  from  Massowah  to  Khartum  the  average  is  86°; 
Tinnevelly,  India,  has  an  average  temperature  of  84.3°,  and,  finally, 
the  average  at  Wyndham,  northwest  Australia,  is  84.6°  F. 

In  the  annual  north-south  progress  of  the  seasons  the  75°  isotherm 
sweeps  nearly  the  entire  continent  (figs.  9a  and  96) .  The  coohng  effects 
of  the  sea  and  of  the  highlands  are  to  be  seen  in  the  curving  of  the  iso- 
therms. As  a  whole,  however,  the  interior  has  relatively  high  tem- 
peratures. Table  6  gives  some  of  the  highest  shade  temperatures 
reported  in  Australia  previous  to  1912,  and  probably  among  the 
highest  reported  anywhere.  In  table  7  are  presented  data  relative  to 
the  temperature  at  several  stations,  mainly  in  regions  of  small  rainfall. 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA.  19 

Table  6. — Maximum  shade  temperatures  previous  to  1912,  together  with  rainfall. 


Localities. 

Rainfall, 
inches. 

Temp.,°F. 

William  Creek 

Marble  Bar     

5.46 
13.88 
18.9 
10.05 
14.44 

119.0 
120.5 
122.2 
123.2 
127.0 

Walgott 

Bourke 

Table 

7. — Temperature, 

F.* 

Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

William  Creek: 

82.9 
88.9 
77.0 
119.0 
53.0 
24.4 

0.0 

81.9 
88.6 
77.0 
118.0 
53.2 
23.8 

0.0 

77.6 
83.6 
72.8 
114.8 
51.7 
14.4 

0.0 

74.1 
81.3 
67.0 
116.3 
45.1 
11.1 

0.0 

78.8 
83.1 
72.2 
114.4 
47.1 
19.8 

0.0 

82.8 
89.4 
77.3 
115.0 
52.5 
21.6 

0.0 

82.0 
88.2 
76.6 
114.3 
51.0 
21.7 

0.0 

78.3 
84.5 
73.5 
117.0 
49.1 
13.4 

0.0 

74.1 
83.0 
69.1 
113.6 
46.4 
10.1 

0.0 

77.6 
84.3 
73.8 
115.0 
48.2 
15.6 

0.0 

76.4 
81.1 
71.4 
110.4 
46.0 
14.4 

0.0 

75.8 
79.8 
70. 0 
111.1 
46.5 
14.6 

0.0 

73.4 
77.2 
70.0 
110.9 
48.6 
9.1 

0.0 

69.9 

74.8 
65.2 
108.0 
44.8 
6.0 

0.0 

73.0 
77.4 
69.8 

105.0 
43.4 

110.2 

0.0 

1 

67.3 
70.0 
63.5 
101.5 
39.0 
3.0 

0.1 

66.4 
69.6 
62.0 
98.0 
39.1 
2.8 

0.2 

66.4 
71.2 
62.4 
98.0 
42.0 
2.9 

0.0 

63.9 
69.3 
59.2 
98.0 
39.6 
0.8 

0.0 

66.4 
71.6 
60.5 
101.4 
37.0 
3.2 

0.3 

59.2 
62.3 
55.0 
93.2 
29.2 
0.3 

5.0 

58.4 
61.3 
54.3 
91.5 
31.7 
0.1 

5.2 

59.7 
63.6 
56.4 
91.2 
35.0 
0.1 

0.8 

57.7 
61.2 
54.2 
88.3 
36.9 
0.0 

0.6 

58.8 
61.6 
55.0 
92.0 
34.5 
0.0 

2.8 

54.0 
58.4 
49.2 
81.5 
27.5 
0.0 

9.9 

52.7 
57.0 

48.7 

86.0 

27.3 

0.0 

12.6 

54.6 
57.9 
50.6 
80.8 
32.2 
0.0 

3.9 

53.4 
57.2 
49.8 
76.0 
32.5 
0.0 

2.8 

53.6 
56.5 
49.4 
76.8 
32.5 
0.0 

6.5 

52.3 
55.6 

48.4 

82.5 

25.8 

0.0 

15.3 

50.9 
54.0 

47.7 

78.0 

28.3 

0.0 

18.5 

52.9 
55.1 
50.4 
75.2 
31.4 
0.0 

7.2 

51.6 
55.7 
49.0 
74.0 
32.0 
0.0 

5.6 

52.0 
54.3 
49.5 
80.0 
31.4 
0.0 

11.0 

56.4 
61.2 
53.4 
95.8 
25.3 
0.1 

8.8 

54.8 
60.6 
51.9 
90.5 
29.6 
0.0 

12.8 

55.8 
60.2 
53.0 
86.4 
32.0 
0.0 

4.1 

54.0 
58.3 
49.9 
85.0 
32.3 
0.0 

3.4 

54.8 
57.7 
51.5 
87.0 
32.1 
0.0 

7.0 

62.5 
65.8 
56.8 
101.0 
34.5 
2.1 

1.3 

60.7 
63.6 
55.6 
98.2 
34.0 
1.2 

3.1 

60.5 
63.2 
56.0 
94.0 
38.0 
0.5 

0.5 

57.0 
61.0 
52.0 
90.7 
32.7 
0.0 

1.6 

59.9 
63. S 
55. S 
95.0 
32.4 
0.6 

2.7 

70.3 
75.0 
62.7 
110.5 
37.0 
8.8 

0.2 

68.7 
73.6 
61.1 
107.0 
37.0 
7.2 

0.2 

66.8 
71.4 
59.3 
106.3 
39.6 
4.7 

0.1 

62.0 
69.6 
55.2 
102.2 
36.0 
1.6 

0.4 

65.2 
71.2 
61.2 
101.0 
38.2 
3.0 

0.6 

77.0 
83.3 
71.8 
114.2 
41.0 
16.4 

0.0 

75.5 
81.7 
67.6 
111.5 
42.0 
15.2 

0.0 

72.0 
77.1 
65.3 
108.8 
43.0 
9.4 

0.0 

67.0 
72.1 
60.8 
113.5 
40.8 
5.1 

0.0 

72.3 
77.8 
68.0 
110.2 
38.2 
10.6 

0.0 

81.5 
85.4 

68.6 

76.5 

116.4 
48.0 
22.9 

0.0 

80.2 
83.8 
73.9 
114.2 
47.5 
21.9 

0.0 

75.9 
80.1 
70.7 
114.2 
48.0 
12.9 

0.0 

71.1 

77.4 
65.8 
114.2 
43.0 

8.8 

0.0 

77.4 
81.7 
71.0 
113.0 
47.0 
18.4 

0.0 

119.0 
25.3 
114.0 

40.6 

67.3 

li8."6 
27.3 
108.5 

52.6 

66.2 

117.0 
31.4 
67.4 

16.6 

63.0 
65.2 
60.9 
116.3 
32.0 
43.5 

14.4 

65.8 
67.7 
64.2 
115.0 
31.4 
81.4 

30.9 

Mean  No.  of  days  over  90 

Mean  No.  of  nights  under 

40     

Farina: 

Mean     

Highest  mean         

Lowest  mean 

Absolute  maximum 

Absolute  minimum 

Mean  No.  of  days  over  90 

Mean  No.  of  nights  under 

40 

Point  Augusta: 

Mean  No.  of  days  over  90 

Mean  No.  of  nights  under 

40 

Adelaide: 

Absolute  maximum 

Mean  No.  of  days  over  90 

Mean  No.  of  days  under 

40                   

Kalgoorlie: 

Mean                 

Highest  mean            

Lowest  mean           

Absolute  maximum      . .    .  . 

Absolute  minimum      .... 

Mean  No.  of  days  over  90 

Mean  No.  of  nights  under 

40                       

1 

1 

*  Supplied  by  the  Commonwealth  Bureau  of  Meteorology,  Central  Bureau,  Melbourne. 


20  PLANT    HABITS   AND    HABITATS   IN   THE 

The  number  of  days  during  which  the  shade  temperature  may  reach  or 
exceed  90°  F.  in  the  central  portion  of  Australia  may  be  very  considerable 
(table  7).  For  example,  in  the  northern  part  of  Western  Australia  the 
maximum  shade  temperature  sometimes  exceeds  90°  for  days  or  weeks  at 
a  tune.  At  William  Creek,  South  Australia,  there  are,  on  the  average, 
114  days  in  each  year  when  the  thermometer  registers  90°  or  over. 
When  it  is  recalled  that  the  relative  humidity  of  the  air  is  a  function  of 
the  temperature,  the  significance  of  such  long-continued  high  tempera- 
tures for  plant  growth,  more  especially  in  the  dry  interior,  is  apparent. 

The  daily  range  in  the  temperature  of  the  air  is  especially  striking  in 
regions  where  the  rainfall  is  relatively  small.  Thus  in  20  stations  in 
Western  Australia  and  South  Australia,  whose  average  precipitation  is 
8.5  inches,  the  average  daily  range  of  temperature  is  37°  F. 

Winds. 

The  action  of  air  currents,  both  directly  and  indirectly,  upon  plants 
and  their  environment  is  of  the  greatest  importance,  especially  in  dry 
regions.  One  of  the  pronounced  characteristics  of  such  regions  is  the 
prevalence  of  winds.  With  little  vegetation  to  impede  their  way, 
they  are  nearly  always  blowing.  During  the  seasons  of  rains  this  is  of 
comparatively  little  moment  to  plants,  but  with  the  return  of  dry 
conditions,  particularly  during  the  summer,  the  winds  operate  to  in- 
crease the  drought  in  a  marked  degree;  and  even  in  situations  more 
or  less  remote  from  the  dry  interior  the  ill  effects  of  the  ''desert"  winds 
can  frequently  be  seen  in  the  withering  of  vegetation  of  all  kinds. 
Thus,  in  southern  South  Australia,  distant  from  the  dry  interior  over 
250  miles,  such  winds  are  experienced  occasionally  and  sometimes  are 
disastrous. 

Evidences  of  wind  action  are  not  wanting  in  other  directions. 
Crescentic-shaped  dunes  near  Oodnadatta,  the  surfaces  of  which  bear 
ripple  marks,  and  the  moving  of  fine  earth  in  other  places,  as  at  Copley, 
where  fences  are  buried  beneath  it,  are  further  indications  that  the 
winds  are  active  as  well  as  forceful.  The  flattening  of  the  "gibbers," 
which  make  up  the  desert  pavement  characteristic  of  large  areas  in  the 
central  portion  of  the  continent,  may  also  be  an  indirect  result  of  wind 
action.  The  pavement  itself  is  the  result  of  the  removal  by  the  wind 
of  the  finer  soil  particles,  and,  in  fact,  it  is  generally  recognized  as 
probable  that  the  wind  is  a  very  important  agent  of  erosion  in  the  dry 
nterior,  as  eyidenced  in  a  great  variety  of  ways  (Jutson,  1914:142). 
Subterranean  Environment. 

The  leading  habitats  of  the  desertic-semiarid  regions  are  apparently 
few  in  number.  They  are  characterized  and  may  be  distinguished  by 
their  physical  nature  and  chemical  content,  as  well  as  by  their  physio- 
graphical  relations.  Thus,  there  are  salt  spots,  salt  plains,  and  salt 
slopes  in  whieh  the  soil,  often  of  rather  fine  structure,  carries  an  excess 
of  salts.     Such  saline  areas  are  often,  but  apparently  not  always, 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  21 

associated  with  poor  surface  drainage.  These  areas  are  so  numerous 
and  may  be  so  extensive  that  they  constitute  a  very  important  portion 
of  the  habitats  of  the  interior.  The  non-sahne  habitats  are  to  be  dis- 
tinguished from  one  another  in  part  by  physical  and  chemical  com- 
position and  in  part  by  their  phj^siographical  relations.  The  leading 
differences  between  them,  at  least  from  a  biological  point  of  view,  rest 
mainly  on  differences  in  their  water-content  and  (probably  also  asso- 
ciated with  this)  on  their  relative  temperatures.  Thus  there  are 
stream-ways  and  flood-plains  and  often  terraces,  plains  of  several 
levels.  The  first  two  are  subject  to  occasional  flooding,  but  the  latter 
may  or  may  not  receive  water  by  seepage  from  still  higher  ground. 
Other  plains  may  occupy  the  highest  elevations  and  thus  may  have 
water  relations  quite  different  from  those  of  the  plains  last  mentioned. 
The  plains  may,  or  may  not,  be  protected  against  wind  erosion  by  a 
covering  of  coarse  stones,  "gibbers."  There  are  also  hills  and  low 
mountains  and  the  slopes  of  these.  Of  the  hills,  the  moving  or  sta- 
tionary dunes  constitute  important  features  of  the  physiography  of  the 
dry  interior.  Between  the  sandy  ridges  there  are  often  fiat ' '  clay-pans" 
which  have  interesting  features  of  their  own.  Ina,smuch  as  the  species 
to  be  found  in  these  habitats  are  often,  possibly  largely,  characteristic 
of  them,  the  subaerial  environment  constitutes  a  very  important  factor 
in  the  environment  as  a  whole. 

The  subaerial  environment  of  plants  thus  has  interesting  connection 
with  surface  geology  and  its  history  would  be  that  of  physiography. 
Without  entering  into  a  discussion  of  this  phase  of  the  matter,  however, 
it  will  be  instructive  to  note  certain  characteristics  of  the  dynamics  of 
the  general  subject.  Thus,  Howchin  and  Gregory  (1909 :  103)  point  out : 

"An  inland  basin,  like  that  of  Lake  Eyre,  can  not  get  rid  of  its  worn-down 
material,  such  as  occurs  when  the  drainage  of  the  country  flows  into  the  sea, 
whilst  from  a  deficiency  of  moisture  vegetation  is  scarce  and  the  soil  is  but 
loosely  held  together.  From  this  cause  the  soil  and  sand  are  constantly  on 
the  move,  and  with  the  ever  accumulating  products  of  waste,  the  highest 
hills  are  gradually  covered  by  drift,  and  the  country  is  ultimately  buried  under 
its  own  ruins." 

But  the  region  of  the  sandhills  is  not  confined  to  such  a  depressed 
area  as  the  great  central  basin.  Thus  D.  W.  Carnegie  (1898:178) 
describes  in  a  very  vivid  way  a  sand  plain-sandhill  region  in  central 
Western  Australia,  nearly  200  miles  across  in  a  straight  line.  Here  the 
general  level  of  the  country  is  considerably  above  sea-level,  but  the 
drainage  is  inland,  or  at  any  rate  not  directly  to  the  sea,  and  it  can 
possibly  be  described  as  being  undeveloped.  Without  going  into  the 
subject  much  further,  another  region  can  be  mentioned  having  an 
accumulation  of  detritus  (and  sand  is  here  especially  in  mind),  where 
the  drainage  is  not  well  defined.  This  is  the  Ooldea  sandhill  region. 
Here  are  sand  ridges  of  prominence  which  alternate  with  narrow  flats 
over  a  region  about  50  miles  wide.    Apparently  the  rains  are  absorbed 


22  PLANT    HABITS   AND   HABITATS   IN   THE 

where  they  fall,  as  there  are  no  appearances  of  washing  and  the  main 
instrument  of  detrital  transportation  is  the  wind,  but  owing  to  the 
fairly  abundant  vegetation,  as  will  be  described  below,  the  moving  of 
the  sand,  except  where  the  vegetation  has  been  disturbed,  is  not  an 
important  matter. 

A  notable  class  of  plant  habitats  is  that  associated  with  an  excessive 
amount  of  salts  of  whatever  kind  in  the  soils.  The  immediate  occasion 
of  the  accumulation  of  the  salts  is  also  in  part  inadequate  drainage,  but 
coupled  with  this  are  high  evaporation  and  small  rainfall. 

Beds  of  gypsum,  hydrous  calcium  sulphate,  and  of  travertine,  or 
desert  limestone,  calcium  carbonate,  are  frequently  to  be  found  in  the 
dry  regions.  In  certain  regions  outside  of  Australia,  at  least,  travertine 
is  an  important  feature  of  the  environment  of  plants  in  that  it  is  not 
easily  penetrable  by  water  and  constitutes  a  fairly  dry  hardpan  as  a 
subsoil.  By  travertine  is  meant  "a  deposit  of  carbonate  of  lime,  laid 
down  on  the  surface  of  the  ground  by  evaporating  water  containing  the 
substance  in  solution"  (Jutson,  1914:228).  In  many  places  the  traver- 
tine is  covered  by  soil  and  thus  constitutes  a  subsoil.  In  appearance 
the  travertine  strongly  resembles  the  ''caliche"  of  the  more  arid 
portions  of  the  United  States,  and  is  probably  the  same  substance. 
The  exact  soil  horizon  where  the  limestone  is  formed  is  in  dispute 
(Livingston,  1906:8).  In  place  of  its  being  deposited  on  the  surface  of 
the  soil  it  may  be  deposited  at  the  evaporating  surface,  which,  in  such 
an  arid  country  as  southern  Arizona,  at  least,  probably  lies  somewhat 
below  that  of  the  soil  itself. 

The  nature  of  the  soil  is  another  important  factor  of  the  subaerial 
environment.  It  is  dependent  on  the  nature  of  the  underlying  rocks 
from  which  the  soil  was  derived  by  various  geologic  agencies.  As  an 
important  feature  of  the  environment  of  plants  it  is  not  confined  to 
regions  of  small  rainfall,  but  is  to  be  found  in  the  more  moist  regions  as 
well.  Thus  Osborn  (1914 : 1 13)  observes  in  the  vegetation  of  the  Mount 
Lofty  Ranges  near  Adelaide  that — 

"The  second  range  of  foothills,  rising  about  800  feet  to  a  plateau,  presents 
several  markedly  distinct  types  of  vegetation  which  appear  to  be  correlated 
with  the  geological  formation.  The  slate  hills  are  covered  with  grassland  and 
scattered  'gums,'  having  a  parklike  appearance.  The  absence  of  under- 
growth and  the  maintenance  of  a  sward  may  be  partly  due  to  grazing,  but  all 
the  difference  observable  can  not  be  attributed  to  this  cause.  Grass  is  almost 
entirely  absent  from  the  quartzite  hills,  which  are  covered  by  a  scrub  of  many 
species  of  shrubby  plants." 

Jutson  (1914:58),  speaking  of  the  vegetation  of  the  central  or  salt- 
lake  division  of  Western  Australia,  which  is  arid  or  semi-arid,  says : 

"[It  is]  divided  into  two  main  groups,  viz :  that  growing  on  the  basic  and  that 
on  the  granitic  rocks;  the  former  being  stronger  and  of  a  more  varied  character 
and  the  latter  often  or  mainly  of  a  stunted  and  monotonous  type,  except  that 
in  its  annuals  or  small  shrubs  there  is  often  both  variety  and  beauty." 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA.  23 

Temperature,  Moisture,  and  Aeration  Conditions  of  the  Soil. 

The  course  of  the  moisture,  aeration,  and  temperature  conditions  of  the 
soil  are  of  very  great  biolgical  importance,  but,  unfortunately,  so  far  as 
Australia  is  concerned,  only  meager  data  are  to  be  had  respecting  them. 
From  studies  made  elsewhere  (which  are  also  few)  something  of  their 
relation  to  the  general  problems  with  which  this  study  in  part  deals  may 
be  drawn ;  and  the  interest  here  lies  mainly  in  the  results  touching  the 
soils  of  regions  having  a  small  rainfall.  As  is  well  known,  the  three 
conditions  above  mentioned  are  intimately  related  and  it  may  be 
remarked  that  in  consequence  a  modification  of  one  brings  changes  in 
the  rest.  It  is  also  possibly  true  that,  as  to  the  moisture  of  the  soil 
and  its  temperature,  the  maximum  of  variability  finds  its  apex  in  dry 
climates. 

The  moisture  conditions  of  the  soil  are  dependent  on  a  great  variety 
of  factors,  among  which  may  be  mentioned  the  amount  of  rainfall,  the 
physical  nature  of  the  soil,  atmospheric  conditions  relative  to  evapora- 
tion, and  the  plant  cover. 

The  amount  of  water  which  a  given  soil  is  capable  of  holding  is 
related  to  the  physical  nature  of  the  soil  and  according  to  Briggs  and 
Shantz  (1912:31)  varies  from  23.2  to  69.5  per  cent  of  the  dry  weight  of 
the  soil.  The  smaller  amount  is  that  retained  in  coarse  sand  and  the 
larger  amount  is  that  retained  in  clay  loam,  in  both  instances  in  op- 
position to  the  force  of  gravity  when  free  water  drainage  is  provided. 
Not  all  of  the  water  of  such  saturated  soils,  however,  is  available  for  the 
use  of  plants.  Thus  the  same  authors  (1911:217)  show  that,  as  con- 
cerned the  species  experimented  with,  the  amount  of  water  possible  of 
absorption  previous  to  wilting  varied  with  the  character  of  the  soil,  but 
was  considerably  less  than  the  maximum  water-content  of  the  soil. 
Thus,  in  fine  sand  the  plant  used,  Kubanka  wheat,  absorbed  97.01  per 
cent;  in  fine  sandy  loam  it  absorbed  90.34  per  cent;  in  clay  loam  it 
absorbed  83.7  per  cent  of  the  water  held  by  these  soils  when  in  a  good 
state  of  tilth.  At  the  time  of  wilting,  therefore,  there  is  in  the  soil  a 
certain  water-residue  which  varies  with  the  nature  of  the  soil. 

It  would  be  of  interest  to  know  for  how  long  a  period,  in  dry  central 
Australia  especially,  there  is  sufficient  water  in  the  soils  for  the  use  of 
plants.  In  Southern  Arizona  some  attention  has  been  paid  to  this 
phase  of  the  problem.  At  Tucson,  for  example,  Livingston  (1906:72) 
has  found  that  at  a  depth  approximating  0.5  meter  there  is  possibly 
always  sufficient  moisture  for  absorption  by  roots.  At  least  the  upper 
soils,  on  the  other  hand,  are  air-dry  in  the  arid  foresummer,  when  they 
may  contain  not  over  6.5  per  cent  of  their  dry  weight  of  water  (Shreve, 
1914:21).  The  soil  referred  to  is  a  fine,  brown  clay  and,  from  the  work 
of  Briggs  and  Shantz,  it  would  not  be  expected  that  the  plants  could 
extract  from  it  more  than  85  to  90  per  cent  of  its  water-content,  leaving 
a  non-available  moisture  content  of  10  to  15  per  cent.     Therefore,  the 


btate 


24  PLANT   HABITS   AND    HABITATS    IN   THE 

amount  of  moisture  in  the  soil  reported  on  by  Shreve  could  be  con- 
siderably below  that  available  for  plants.  Accordingly  the  arid  fore- 
summer  in  southern  Arizona  constitutes  very  largely  a  resting  season  for 
plants.  Since  this  season  comprises  about  3  months  without  rain,  it 
can  be  concluded  that  as  long,  or  longer,  rainless  periods  as  occur  in  the 
dry  parts  of  Australia  may  operate  to  bring  about  a  condition  of  ex- 
treme soil  dryness  and  that  under  such  circumstances  only  in  favorable 
situations,  or  in  favorable  soils,  or  in  species  which  reach  to  deeply 
placed  soil  moisture,  or  which  have  a  water-balance,  can  vegetational 
activities  be  carried  on. 

Studies  on  the  relation  between  the  moisture-content  of  the  soil  and 
the  condition  of  permanent  wilting  of  plants  indicate  that  all  species 
wilt  at  approximately  the  same  moisture-content  in  the  same  soil,  other 
conditions  being  equal.  Thus,  contrary  to  previously  accepted  belief, 
plants  native  to  dry  regions  are  unable  "to  reduce  the  water-content 
of  the  soil  to  a  lower  point  than  is  reached  by  other  plants  at  the  time  of 
wilting"  (Briggs  and  Shantz,  1912:235). 

Although  possibly  the  largest  percentage  of  water  escapes  from  the 
soil  through  evaporation  from  its  surface,  a  very  considerable  amount  is 
lost  by  reason  of  transpiration  from  the  plant  shoot.  This  goes  on 
until  the  limit  of  water  loss  is  reached  only  by  the  establishment  of  an 
equilibrium  between  air  and  soil,  and  the  final  result  is  the  same  as  if 
the  air  and  soil  were  in  direct  contact  (Briggs  and  Shantz,  1912:  20). 
Not  only  does  the  upper  soil  layer  lose  moisture  through  the  plant  cover, 
but  the  deeper  layers  as  well  become  dry  by  the  same  means.  Thus 
it  has  been  determined  (Alway,  McDole,  and  Trumbull,  1919:185) 
that  the  moisture  of  the  subsoils  may  be  greatly  reduced  through  the 
action  of  deeply  rooted  plants — that  is,  whose  roots  are  5  meters  or  less 
in  length.  Where  such  deep-rooted  perennials  are  wanting,  the  sub- 
soil remains  moist. 

Aeration  of  the  Soil. 

The  aeration  of  the  soil  is  an  environmental  factor  of  plants  of  much 
consequence,  although  it  is  measured  with  difficulty  and  there  appears 
to  be  no  way  of  expressing  it  concretely  or  exactly.  Data  regarding 
this  phase  of  environment,  therefore,  are  largely  wanting,  but  it  is 
known  in  a  general  way  that  the  soils  of  the  dry  regions  are,  as  a  whole, 
well  aerated.  This  follows  from  the  known  conditions  directly  affect- 
ing air-movements  in  soils.  Among  these  the  following  may  be  men- 
tioned: Size  of  the  soil  grains;  compactness  of  the  soil;  amount  of 
moisture  in  the  soil;  winds  and  differences  in  barometric  pressure; 
temperature  of  the  air  and  of  the  soil  itself;  the  plant  cover. 

The  composition  of  the  soil  is  also  an  important  feature  in  its  aera- 
tion. In  the  upper  soil  layers  the  atmosphere  of  the  soil  usually  has 
about  the  same  composition  (except  possibly  as  to  moisture-content) 
as  the  atmosphere  immediately  above  it.     Under  conditions  of  re- 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA.  25 

stricted  movement  of  the  air  within  it,  however,  it  contains  less  oxygen, 
but  a  greater  percentage  of  nitrogen  and  carbon  dioxide.  Where 
such  conditions  obtain,  molecular  and  not  molar  gas-movement  takes 
place,  gaseous  exchange  is  relatively  slow,  and  soil  aeration  is  least 
favorable  for  aerobic  organisms.  So  far  as  the  soils  of  arid  regions 
are  concerned,  possibly  the  most  usual  cause  of  poor  aeration,  in 
both  meanings  as  above  presented,  lies  in  the  puddling  following  rains. 
Under  such  conditions  the  surface  is  compacted,  the  soil  spaces  are 
filled  with  water,  and  mass  air-movement  ceases.  Where  this  is  ac- 
companied by  relatively  high  soil-temperatures  the  amount  of  oxygen 
in  the  soil  atmosphere  rapidly  decreases  and  that  of  carbon  dioxide 
rapidly  increases,  following  the  respirational  activities  of  soil  organisms 
of  all  kinds.  There  follow  differential  reactions  by  which  the  course 
of  development  may  be  and  in  certain  species  certainly  is  determined. 
Under  extreme  conditions  of  poor  aeration  such  may  become  a  factor 
limiting  the  survival  of  a  species  in  a  given  habitat. 

Temperature  of  the  Soil. 

Few  data  on  the  temperature  of  the  soil,  particularly  as  to  the  more 
arid  regions  of  Australia,  are  to  be  had.  However,  the  general  fea- 
tures of  the  course  of  the  soil-temperature  in  arid  regions  are  fairly 
well  known.  The  temperature  of  the  soil  varies  with  a  variation  in 
the  physical  character  of  the  soil,  with  its  moisture-content,  and  with 
the  depth.  Possibly  no  environmental  factor  is  of  greater  importance 
to  plant  life  than  this  one. 

Observations  on  the  temperature  of  the  soil,  made  at  the  Desert 
Laboratory  (Cannon,  1911 :  20),:will  illustrate  the  course  of  the  tempera- 
ture of  the  soil  in  a  semi-arid  climate.  The  records  referred  to  relate 
to  the  temperature  taken  at  two  depths,  15  and  30  cm.,  by  means  of 
thermographs.  At  the  lesser  depth  the  daily  variation  in  temperature 
is  about  8°  to  12°  F.  and  the  maximum  annual  variation  is  about  69°  F. 
The  period  of  maximum  temperature  coincides  with  that  of  the  highest 
summer  temperature  and  immediately  precedes  the  rains  of  that  sea- 
son. With  the  coming  of  the  rains  of  summer  the  soil-temperature 
immediately  falls  and  it  continues  to  drop  gradually  until  somewhat 
past  midwinter,  when  the  upward  movement  begins.  The  rise  is 
gradual  until  the  last  of  March,  when  it  is  somewhat  accelerated,  and  by 
May  the  temperature  of  the  soil  is  nearly  that  of  midsummer. 

There  are,  therefore,  approximately  3  months  each  year,  the  arid 
foresummer,  in  which  high  soil-temperatures  occur  at  a  depth  of 
15  cm.  The  maximum  temperature,  depth  15  cm.,  observed  was 
105°  F.  (40.56°  C.)  and  the  minimum  temperature  at  that  depth  was 
found  to  be  34°  F.  (1.11°  C).  The  temperatures  of  the  soil  at  a  depth 
of  30  cm.  have  many  features  characteristically  different  from  those  of 
the  lesser  depth.  Thus  the  daily  range  in  temperature  is  2°  to  4°  F. 
and  the  annual  variation  is  about  30°  F.     The  ma^iimum  temperature 


26 


PLANT   HABITS   AND    HABITATS   IN   THE 


recorded  for  30  cm.  depth  was  99°  F.  (37.22°  C.)  and  the  minimum 
was  44°  F.  (6.67°  C).  The  yearly  course  of  the  soil-temperatures  for 
this  depth  is  as  follows:  Beginning  with  high  temperatures  of  late 
summer,  just  before  the  rains,  the  temperature  drops  with  the  rains 
and  continues  the  downward  movement  until  March,  when  a  fairly 
rapid  rise  begins  and  persists  until  the  rains  of  midsummer. 

Additional  records  of  60  cm.  and  120  cm.  depths,  unpublished,  show 
noteworthy  features,  some  of  which  are  as  follows :  In  neither  case  is 
there  a  daily  variation  determinable  by  the  apparatus  employed.  In 
both  of  the  greater  depths  the  maximum  temperatures  are  attained 
(as  at  the  two  lesser  depths)  just  before  the  rains  of  midsumm:r.  At 
a  depth  of  60  cm.  the  maximum  temperature  observed  was  89°  F. 
(31.67°  C.)  and  at  a  depth  of  120  cm.  the  maximum  was  79°  F. 
(26.11°  C).  The  minimum  temperature  at  a  depth  of  120  cm.  was 
56°  F.  (13.33°  C),  and  the  annual  range  was  observed  to  be  24°  F. 
The  course  of  the  temperature  at  this  depth  following  the  rains  of 
summer  is  downward  until  late  in  winter,  when  it  gradually  rises  until 
midsummer.  Thus  the  quick  temperature  rise  in  spring  characteristic 
of  the  soil  at  a  depth  of  15  cm.  does  not  occur  at  the  greater  depths. 

The  soil  of  which  the  temperature  at  a  depth  of  15  cm.  and  30  cm. 
was  reported  on  in  the  preceding  paragraph  is  an  adobe  clay,  and 
that  of  which  the  temperature  at  greater  depths  was  characterized 


Fig.  8a. — Mean  annual  evaporation  in  Australia,  after  Hunt. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


27 


above  was  of  clay  with  an  admixture  of  small  stones.  Soils  of  other 
compositions,  especially  of  other  physical  properties,  would  give  other 
results.  Thus,  Hilgard  (1906 :  306) ,  quoting  Wollny,  states  that  different 
soils  have  summer  and  winter  temperature  properties  as  follows:  In 
summer  the  sandy  soils  are  warmest,  with  humous,  lime,  and  loam  soils 
following  in  the  order  named.  In  winter  the  following  order  in  this 
regard  obtains:  humous,  lime,  loam,  and  sandy  soils.  Sandy  soils, 
at  least  the  superficial  layers,  in  summer  and  in  the  desert,  become 
intensely  hot,  according  to  Hilgard,  but  at  the  same  time  they  allow  the 
existence  of  moisture  at  a  depth  of  10  to  12  inches  below  the  surface. ' 
Clay  soils  in  the  same  regions,  "being  usually  in  a  compacted  condi- 
tion, will  show  a  lower  surface  temperature  and  will  be  warmer  and 
drier  at  a  depth  at  which  sand  will  still  retain  abundant  moisture  and 
be  comparatively  cool." 

Certain  additional  features  concerning  the  temperature  of  the  soil 
should  be  mentioned.  It  should  be  said  that  the  position  of  the  sur- 
face relatively  to  the  incident  heat  rays  is  of  some  importance.  Thus, 
as  is  well  known,  the  sun  of  winter  is  less  effective  than  that  of  summer, 
and  slopes  may  be  warmer  or  colder,  depending  on  their  relation  to  the 
direction  of  the  rays  of  heat  impinging  their  surfaces.  Only  surfaces 
lying  at  an  angle  of  90°  to  the  incident  rays  receive  the  maximum  heat. 
When  the  angle  is  30°  the  amount  of  heat  is  about  half  the  maximum, 
and  it  rapidly  falls  with  sharper  angles  (Cannon,  1915^:  213),  so  that  at 
15°  from  the  incident  rays  it  is  only  about  8.5  per  cent  of  the  maximum. 


Fig.  86. — Average  yearly  temperatiire  of  Australia,  after  Hunt. 


28 


PLANT   HABITS   AND   HABITATS   IN   THE 


In  the  preceding  summary  of  temperature  differences  characteristic 
of  different  depths  of  soil,  actual  temperatures  only  were  considered; 
but  another  point  of  view,  which  is  instructive,  can  be  held  by  a  summa- 
tion or  integration  of  the  temperatures,  month  by  month,  for  different 
depths.  Reference  is  here  made  to  a  depth  of  15  cm.  and  30  cm.  and, 
in  addition,  that  of  2.6  meters  is  included  for  comparison.  As  a 
whole,  it  appears  that  there  is  a  greater  amount  of  heat  at  30  cm.  than 
at  15  cm.,  although  the  latter  has  the  higher  maximum.  And  it  ap- 
pears that  the  rains  of  summer  cause  a  sharp  fall  in  the  total  heat, 
but  that  in  the  rainless  early  autumn  the  total,  if  not  the  monthly 
maximum,  temperatures  recover  and  the  final  drop  in  heat  comes  only 
with  mid-autumn.  The  relative  amount  of  heat  at  a  depth  of  15  cm. 
and  at  a  depth  of  30  cm.  is  surprisingly  close.  It  is  only  with  con- 
siderably greater  depth  that  a  marked  falling  off  in  the  total  heat  is  to 
be  found.  Finally,  it  appears  that  the  total  amount  of  heat  is  greatest 
during  January  at  a  depth  of  2.6  meters. 

It  will  be  noted  that  the  soil  depths  above  used  in  the  studies  on 
temperature  were  relatively  great.  Higher  temperatures  are  known 
to  occur  at  less  depths.  Thus,  Coville  and  MacDougal  (1903:41) 
report  a  temperature  of  111°  F.  (43.89°  C.)  in  volcanic  sand  and  alluvial 
deposit  at  a  depth  of  5  cm.  and  cite  Toumey  to  the  effect  that  "the 
temperature  of  the  soil  at  the  depth  of  one  inch  near  Tucson  reaches 
the  temperature  of  113°  F.  (45.0°  C.)  with  a  mean  average  of  104.9°  F. 


Fio.  9o. — Mean  temperature  of  Australia  for  January,  after  Hunt. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


29 


(40.5°  C.)  for  the  entire  month  of  July."  Even  higher  temperatures 
of  superficial  soils  have  been  reported  (Coville  and  MacDougal, 
q.  v.,  p.  41).  Therefore,  at  one  and  the  same  moment  the  roots  of  spe- 
cies of  deeply  penetrating  root-habit  may,  near  Tucson,  be  subject  to  a 
temperature  stress  of  33.1°  F.  (18  3°  C.)  or  over,  or  more  than  the  total 
maximum  yearly  variation  at  a  depth  of  30  cm. 

Owing  to  the  large  number  of  factors  which  determine  the  tempera- 
ture of  the  soil,  it  is  impossible,  in  the  absence  of  actual  temperature- 
measurements,  to  satisfactorily  adjudge  this  important  feature  of  the 
physical  environment  of  plants.  Hann  (1903 :  43)  states  that  the  daily 
variations  in  temperature  hardly  extend  one  meter  into  the  ground,  and 
that  one  observation  daily  at  greater  depths  suffices  to  give  good  means. 
Conversely,  all  things  being  equal,  it  should  be  possible  to  roughly 
evaluate  the  mean  annual  temperature  of  average  soils  at  a  depth  of 
one  meter  from  the  air  means  of  the  latitude.  At  the  middle  and 
higher  latitudes,  however,  Hann  states  that  the  soil  at  a  depth  of  one 
meter  has  an  annual  mean  about  1°  C.  above  that  of  the  air.  Taking 
the  annual  average  temperature  of  the  air  for  Australian  regions  along 
135°  east  longitude,  as  given  by  Taylor  (1918- :  4),  we  have,  therefore, 
an  estimate  of  the  mean  annual  temperatures  of  the  soil  at  a  depth 
of  one  meter  and  at  different  latitudes.  These  are  given  in  table  8, 
adapted  from  Taylor.     It  will  be  seen  that  at  the  depth  given  and 


Fig.  96. — Mean  temperature  of  Australia  for  July,  after  Hunt. 


30 


PLANT   HABITS   AND   HABITATS   IN   THE 


between  the  extreme  north  and  extreme  south  of  the  continent  of 
AustraHa  there  is  a  difference  of  approximately  27°  F.  in  the  mean 
annual  temperature  of  the  soil. 

It  is  of  interest  to  note  that  the  mean  air-temperatures  in  the  desert 
are  higher  at  parallel  latitudes  than  those  given  by  Taylor  for  longi- 
tude 135°,  and  probably  also  the  mean  temperature  of  the  soil  at  a  depth 
of  3  feet  is  higher  in  the  desert.  Thus,  at  William  Creek,  28°  55'  south 
latitude,  the  yearly  mean  temperature  is  68.6°  F.  (20.33°  C),  which 
is  2.6°  higher  than  at  latitude  30°  along  the  longitude  farther  east, 
as  given  by  Taylor.  The  summer  mean  temperature  of  the  air  and  of 
the  soil  at  William  Creek  also  is  quite  as  high  as  at  latitude  10°, 
and  the  winter  mean  is  quite  as  low ;  in  fact,  it  is  somewhat  lower 
than  the  mean  in  the  southern  extremity  of  the  continent.  Thus,  at 
William  Creek  the  course  of  the  mean  air-temperature  throughout  the 
year,  and  probably  also  of  the  soil  at  a  depth  of  one  meter,  is  continental 
in  its  range. 

Table  8  shows  the  estimated  mean  annual  soil-temperatures,  depth 
one  meter,  at  latitudes  given  and  in  regions  along  135°  east  longitude. 


Table 


Lat.  S. 

Soil  temp. 

Tropic : 

°  F. 

10 

82 

16 

81 

20 

76 

Temperate : 

26 

70 

30 

66 

35 

61 

40 

65 

ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  31 

CERTAIN   CHARACTERISTICS   OF  THE  VEGETATION  OF 
DRY  REGIONS. 

In  external  and  internal  morphology,  as  well  as  in  many  physio- 
logical processes,  the  vegetation  of  regions  having  a  small  rainfall  is 
different  from  that  of  the  humid  regions.  For  instance,  the  shoot  may 
be  greatly  reduced  both  as  to  size  and  surface.  The  constituent 
members  of  the  shoot  may  assume  fairly  vertical  positions.  The 
foliage  may  be  largely  restricted  to  the  ends  of  the  branches,  from  which 
may  arise  a  canopy-form  of  shoot.  The  leaves  may  be  wanting  or  they 
may  be  replaced  by  phyllodia.  Succulency  may  be  found  in  leaf,  shoot, 
and  root,  or  in  any  of  these.  Other  modifications  include  the  rolling 
of  the  leaves  of  grasses,  greatly  elongated  type  of  leaves,  or  phyllodia, 
and  in  some  forms  dissected  leaves  in  which  the  leaflets  or  lobes  may  be 
considered  the  physiological  equivalent  of  leaves.  In  many  species 
the  shoots  are  provided  with  trichomes  of  various  kinds,  which  serve 
as  a  protection  against  rapid  loss  of  water  from  the  surface.  The 
trichomes  may  protect  indirectly  through  the  secretion  of  resinous 
substances,  which  coat  the  surface,  especially  of  young  leaves  or  shoots 
(Collins,  1918:255). 

The  roots  of  xerophytes  are  as  a  rule  deeply  penetrating,  but  this 
is  not  without  exceptions.  Many  forms  with  water-storage  capacity, 
for  example,  have  roots  which  lie  close  to  the  surface  of  the  ground 
(Cannon,  1911).  Also,  perennials  may  have  roots  of  a  dual  habit  in 
that  some  are  superficially  placed,  and  some  may  penetrate  deeply. 

The  leaves  (or  their  equivalent)  of  xerophytes  are  leathery  in  texture. 
An  examination  of  their  structure  shows  certain  characteristic  features, 
among  which  may  be  mentioned  the  following:  The  outer  wall  of  the 
epidermal  cells  may  be  heavy  and  heavily  cutinized  and  sclerenchyma 
is  well  developed.  There  is  usually  found  palisade  tissue  and  few 
intercellular  spaces.  The  stomata  are  protected  in  various  ways,  as  by 
being  placed  at  the  bottom  of  tubes,  in  which  case  the  walls  of  the  tubes 
may  be  cutinized.  Storage  cells  for  water,  which  in  times  of  need 
yield  water  slowly  to  the  adjacent  cells,  are  often  found.  In  large, 
fleshy  species,  where  the  water-storage  tissue  is  well  developed,  the 
stored  water  may  be  sufficient  to  enable  the  plant  to  live  for  a  period 
exceeding  73  months  in  a  dry  atmosphere  and  without  absorbing 
additional  water  (MacDougal,  Long,  and  Brown,  1915:290). 

As  would  be  expected  from  the  specialization  of  the  structures  of 
xerophytes,  as  well  as  from  the  leading  features  of  their  morphology,  the 
physiological  characteristics  of  the  plants  of  the  desert-arid  regions 
have  many  points  of  interest.  These  are  largely  associated  with  the 
water  relations  of  the  plants;  thus  the  effects  of  dryness  have  been 
followed  in  many  directions.  The  growth-rate  is  less  at  midday,  when 
the  rate  of  transpiration  is  high  and,  relatively  speaking,  the  rate  of 
water  absorption  by  the  plant  is  low  (MacDougal,  1918:59).  The 
progressive  desiccation  of  the  soil  and  of  the  tissues  in  Opuntia  versicolor 


32 


PLANT   HABITS   AND    HABITATS   IN   THE 


is  accompanied  by  a  change  in  the  ''relative  transpiration,"  or  tran- 
spiration power  (relation  between  rate  of  transpiration  and  rate  of 
evaporation) .  Under  dry  conditions  the  t/e  ratio  is  greater  by  day,  but 
under  moist  conditions  it  is  greater  by  night  (Shreve,  E.  B.,  1915:  79). 
The  fluids  of  desert  plants  have  a  high  concentration,  as  determined  by 
Fitting  (1911:209),  Lawrence,  Gortner,  and  Harris  (1916:1).  The 
concentration  of  the  juices  varies  in  relation  to  local  environmental 
conditions.  It  is  least  in  the  aiToyos  and  greatest  in  the  salt  spots. 
For  example,  an  average  of  eight  determinations  of  the  density  of  the 
juices  of  plants  from  the  latter  habitat  gave  37.1  atmospheres.  Table 
9  summarizes  these  results. 

Table  9. — Osmotic  pressure,  in  atmospheres,  of  various  growth-forms  in  five  habitats  of  tht 
Tucson  region  {Harris,  1916 :  81). 


Growth-forma. 

Arroyos. 

Canyons. 

Rocky 
slopes. 

Bajadas. 

Salt  spots. 

Trees  and  shrubs 

Dwarf  shrubs  and  twiners . 
Perennial  herbs 

17.7 
16.6 
13.0 
12.9 

22.4 
21.0 
14.4 
13.0 

22.0 
21.1 
16.8 
15.3 

34.7 
23.9 
19.7 
21.1 

47.9 
34.2 

23.6 

Richards  (1918: 64)  finds  that  a  certain  species  is  more  or  less  suc- 
culent when  growing  under  dry  conditions,  whereas  the  typical  forms, 
under  moist  conditions,  have  thin  leaves.  In  every  instance  the  more 
succulent  form  developed  less  acid  than  the  form  less  succulent. 

The  dryness  of  the  atmosphere  works  immediately  to  influence  the 
formation  of  a  greater  amount  of  cellulose  and  a  lesser  amount  of 
starch  (MacDougal  and  Spoehr,  1918^:247).  Thus  the  polysacchar- 
ides are  converted  into  anhydrides  or  wall  material  under  conditions 
of  aridity,  or  in  succulent  species,  polysaccharides  are  converted  into 
pentosans  or  mucilages.  These  changes,  particularly  the  last,  are  of 
great  physiological  importance  to  the  species,  inasmuch  as  the  "imbi- 
bition "  capacity  of  the  polysaccharides  is  small.  Their  transformation 
from  this  form  into  that  of  the  pentosans  gives  the  increased  capacity 
(of  imbibition)  characteristic  of  the  pentosans,  so  that  without  any 
addition  of  material  to  a  cell,  but  simply  by  the  loss  of  water,  a  change 
takes  place  by  which  the  cell  is  capable  of  absorbing  and  holding  vastly 
greater  proportions  of  water. 

Low  water-content  of  certain  cacti  results  in  a  condition  of  general 
reversion  of  carbohydrates  to  polysaccharides.  The  simpler  sugars,  or 
monosaccharides,  decrease  in  amount  in  the  plants  as  the  water-content 
is  reduced.  With  continued  low  water-content  the  pentosans  increase 
decidedly  (Spoehr,  1918:62). 

It  would  appear,  therefore,  that  dryness  of  itself  may  profoundly 
modify  the  chemical  nature  of  plants  exposed  to  its  influence  and  it  may 
lead,  as  indicated  above,  on  the  one  hand  to  formation  of  wall  material, 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  33 

or  on  the  other  to  that  of  material  capable  of  imbibing  water  in  large 
amounts.  Thus  a  condition  of  succulence  may  be  induced,  and 
possibly  also  the  formation  of  mucilage  cells  frequently  found  in 
xerophytes.  The  presence  of  heavy  cell-walls,  and  possibly  also  the 
condition  of  spininess  characteristic  of  many  plants  of  dry  regions,  may 
thus,  at  least  in  part,  find  a  rational  explanation. 

The  temperatures  of  the  air  and  of  the  soil  are  of  very  great  im- 
portance in  many  physiological  processes  of  xerophytes  as  well  as 
other  types  of  plants.  Certain  of  the  temperature  relations  may  be 
here  mentioned.  For  example,  the  critical  temperatures  for  growth 
are  to  a  degree  specific,  and  on  this  fact  may  depend  in  part  the  charac- 
teristic distribution  of  the  species,  its  time  of  vegetative  and  repro- 
ductive activity,  and,  in  certain  instances,  the  type  of  root-system 
developed  (Cannon,  1914:81,  1914:83,  1915:62,  1915:87,  1915^:211, 
1916:75,  1916^:435,  1917:82).  In  evaluating  the  temperature  of  the 
soil  as  an  environmental  factor  the  critical  temperatures  for  growth  of 
any  given  species  must  be  known,  as  well  as  the  soil-temperatures  at 
the  depth  normally  attained  by  the  roots.  The  total  expected  growth 
during  the  growing  season  with  the  aid  of  these  data  can  be  easily  de- 
termined. In  this  manner  also  we  may  learn  the  relative  efficiency 
of  two  stations  as  regards  any  species,  so  far  as  the  soil-temperature  is 
concerned;  also,  the  biological  significance  of  a  summation  of  soil- 
temperatures  may  be  found  by  the  same  means  (Cannon,  1917: 91). 

As  to  the  immediate  effects  of  temperature,  only  a  few  especially 
applicable  references  need  be  given.  The  osmotic  pressures  increase 
with  an  increase  in  temperature  and  the  rate  at  which  dissolved  sub- 
stances diffuse  through  protoplasm  also  depends  on  temperature.  The 
hydrolysis  of  starch  is  hastened  by  higher  temperatures  up  to  45°  to 
50°  C.  The  acid-content  is  lowered  with  higher  temperatures.  The 
rate  of  gaseous  exchange,  in  respiration,  is  nearly  proportional  to  the 
temperature.  The  maximum  rate  occurs  at  about  40°  C,  and  the 
minimum  at  10°  to  15°  C.  (Palladin,  1917).  The  carbohydrate  equi- 
librium of  Opuntia  sp.  depends  in  part  on  the  water-content  and 
in  part  on  the  temperature  of  the  plant.  An  increase  in  the  tem- 
perature results  in  the  more  rapid  using  up  of  the  available  simple 
carbohydrates,  the  monosaccharides  (Spoehr,  1917:73).  The  rate  of 
water  absorption  in  agar  and  in  biocolloids  increases  in  general  with  a 
rise  in  temperature  up  to  maximum  swelling  of  the  plates,  which  occurs 
near  40°  C.  in  agar  and  somewhat  higher  in  the  biocolloids  (Mac- 
Dougal,  1918:68). 

The  position  taken  in  the  ground  by  the  roots  of  certain  species  has  a 
very  definite  relation  to  the  aeration  conditions  of  the  soil  (Cannon, 
1918: 81)  and  the  distribution  of  cultivated  plants  (Howard  and  How- 
ard, 1915),  as  well  as  certain  species  native  to  a  semi-arid  region  (Can- 
non and  Free,  1917: 178),  may  also  be  directly  related  to  the  root  re- 


34 


PLANT   HABITS   AND   HABITATS   IN   THE 


action  to  conditions  of  poor  soil-aeration.  The  first  noticeable  effect 
of  oxygen  deprivation  to  the  roots  of  Coleus  sp.  is  the  cessation  of  the 
absorption  of  water  (Free  and  Livingston,  1915 :  60).  This  is  followed 
by  a  cessation  of  growth  and  ultimate  wilting  of  the  shoot. 


<^J^//^///^////^/^/^^y/^/////y^^^^ 


Fig.  10.— Chief  physical  divisions  and  geographical  plan  of  South  Australia,  after  Howchin  and 
Gregory,  with  the  6,  10,  and  16  inch  isohyets. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  35 

PHYSICAL  ENVIRONMENT  OF  THE  VEGETATION  OF 
SOUTH    AUSTRALIA. 

PHYSICAL  GEOGRAPHY. 

The  state  of  South  Australia  comprises  about  12.8  per  cent  of  the 
area  of  AustraUa.  It  lies  between  south  latitude  28°  and  about  38°, 
and  longitude  129°  and  141°  east  from  Greenwich.  The  state,  there- 
fore, is  wholly  included  within  the  temperate  zone.  In  latitude 
South  Australia  roughly  corresponds  with  central  Chili,  Argentina, 
and  southern  Africa,  and  in  the  northern  hemisphere  with  Algeria, 
southern  Spain,  and  southern  Italy,  northern  Egypt,  Palestine,  and 
the  most  of  Asia  Minor,  and  northern  China  and  Japan.  So  far  as  the 
climate  is  concerned,  as  will  be  shown  below,  the  state  probably  most 
nearly  resembles  southern  California,  the  Mediterranean  region,  and 
southern  Africa. 

South  Australia  may  be  fairly  \7ell  divided  into  three  physiographic 
general  regions,  as  indicated  in  figure  10,  page  34.  These  may  be 
referred  to  as  the  western  plateau,  the  (central  and  northwestern) 
highlands,  and  the  lowlands  (of  the  south  and  east). 

The  western  plateau  is  an  eastern  continuation  of  the  great  plateau 
of  Western  Australia,  which  embraces  about  half  of  the  land  surface 
of  the  continent.  So  far  as  concerns  the  portion  of  the  plateau  within 
the  borders  of  South  Australia,  it  can  be  divided  into  three  leading 
physiographic  formations,  which  may  be  referred  to  as  the  Bunda 
plateau  or  Nullarbor  plains,  the  Lake  Torrens  plateau,  and  the  desert 
sandstone  tableland. 

The  country  which  lies  along  the  Great  Australian  Bight,  and  extend- 
ing about  150  miles  inland,  constitutes  the  region  known  as  the  Nullar- 
bor plains,  from  its  supposed  treeless  character,  or  Bunda  plateau, 
from  the  native  name  for  the  cliffs.  The  plateau  rises  from  about  250 
feet  at  the  sea  to  800  or  1,000  feet  along  the  northernmost  portion. 
It  is  a  limestone  plain  of  Miocene  age  and  constitutes  an  extension  of 
the  older  plateau  of  Western  Australia. 

The  Lake  Torrens  plateau  lies  to  the  west  of  Lake  Torrens,  or,  more 
exactly,  to  the  west  of  the  great  valley  of  South  Australia.  It  is  of 
limited  extent  and  is  made  up  in  part  of  flat-topped  hills  west  of  Point 
Augusta,  known  as  the  Tent  Hills.  It  attains  its  greatest  width  just 
to  the  west  of  Lake  Torrens  (Howchin  and  Gregory,  1909 :  93)  and  is 
much  older,  geologically,  than  the  Nullarbor  plains,  being  of  the  same 
age  as  the  Flinders  Ranges  (Howchin  and  Gregory,  I.  c). 

The  third  tableland,  the  Desert  Sandstone,  "once  extended  over 
most  of  central  and  northern  Australia.  *  *  *  it  represents  the 
old  land  and  fresh-water  deposits  which  accumulated  after  the  Cre- 
taceous sea  drained  off  from  central  Australia."  The  desert  sand- 
stone tableland  extends  from  Copley  north  and  forms  the  general  fea- 


36  PLANT   HABITS    AND    HABITATS    IN   THE 

ture  of  the  western  side  of  Lake  Eyre.  "The  regular  flat-topped  hills 
represent  the  old  land-levels,  fragments  of  which  have  been  preserved 
from  denudation  by  hard  silicious  beds  that  have  formed  the  protecting 
cappings  for  the  softer  beds  beneath"  (Howchin  and  Gregory,  I.  c). 
At  present  this  formation  is  reduced  to  a  triangle,  of  which  the  base 
abuts  against  the  northern  end  of  the  highlands  of  South  Australia 
(Gregory,  1906:64).  On  the  north  it  extends  apparently  beyond  the 
confines  of  South  Australia  and  on  the  west  it  reaches  to  the  eastern 
end  of  the  Everard  Ranges.  The  desert  sandstone  belongs  to  the 
Upper  Cretaceous  series.    According  to  Jack  (1915:41): 

"The  series  is  made  up  of  sandstone,  grit,  light  to  grey  shale,  and  a  little 
limestone  and,  as  far  as  it  is  possible  to  judge,  has  a  thickness  not  exceeding 
200  feet.  *  *  ♦  Subsequent  to  the  elevation  of  these  beds  striking  hydro- 
chemical  metamorphosism  has  taken  place  under  the  joint  influence  of  light, 
rainfall,  and  warmth,  resulting  in  very  extensive  silicification  of  the  surface 
rocks  *  *  *  largely  responsible  for  the  very  characteristic  topography 
of  the  Upper  Cretaceous  areas.  *  ♦  *  The  presence  of  this  resistant 
capping  of  quartzite,  chert,  or  flint  has  resulted  in  the  formation  of  table- 
topped  hills  and  tablelands.  The  wearing  away  of  the  soft  underlying  shales 
undermines  the  indurated  beds,  which  break  up  to  form  the  stony  mantle  of 
the  *  gibber '  plains,  and  by  its  presence  affords  evidence  of  the  former  extension 
of  the  Upper  Cretaceous  rocks,  even  though  denudation  has  proceeded  so  far 
as  to  leave  the  residual  stones  resting  directly  upon  the  blue  shale  of  the  Lower 
Cretaceous  series." 

The  author  goes  on  to  say  that  the  rounded  form  of  the  "gibbers" 
is  due  to  the  action  of  insolation.  Many  of  the  stones  are  highly 
polished  as  a  result  in  part  from  the  attrition  of  dust  and  sand  blown 
by  the  wind,  and  in  part  from  a  coating  on  their  surfaces  of  a  glaze 
caused  by  the  evaporation  of  siliceous  and  ferruginous  water  on  the 
stones.  This  desert  glaze,  or  varnish.  Jack  states  is  a  feature  common 
to  arid  regions.  Largely  because  of  the  reflection  of  light  from  their 
poUshed  surfaces,  but  also  because  of  their  presence  under  foot,  the 
gibber  plains  present  difficulties  for  the  traveler.  For  example,  Spen- 
cer and  Gillen  (1912:40)  narrate: 

"  A  little  v:ay  to  the  north  of  Oodnadatta  we  passed  on  to  gently  undulating 
country,  with  low-lying,  flat-topped  hills  and  remarkable  plains  covered  with 
small  stones.  Nothing  could  possibly  be  more  desolate  than  these  'gibber 
fields.'  *  *  *  The  horizon  is  shimmering  and  indistinct  and  the  level 
ground  is  co-vered  with  a  layer  of  close-set,  purple-brown  stones,  all  made 
smooth  and  shiny  by  the  constant  wearing  action  of  wind-borne  sand  grains, 
for,  in  winter  especially,  a  strong  southeast  wind  often  blows  all  day  long." 

As  these  excerpts  would  indicate,  the  desert  sandstone  plateau  con- 
stitutes, for  various  reasons,  a  feature  of  the  landscape  of  the  more 
arid  portion  of  South  Australia  that  is  striking  in  the  extreme. 

The  mountains  and  the  hill  country  of  South  Australia  are  of  two 
classes,  geologically  unlike  and  to  a  degree  constituting  separate  physio- 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  37 

graphic  areas.  Of  these,  the  more  ancient,  Archaean,  make  up  the  large 
and  relatively  high  upland  area  in  the  extreme  northwest  portion  of  the 
state,  where  are  the  Musgrave  Ranges  and  others.  Remnants  of  for- 
mer extensive  mountain  ranges,  similar  ancient  rocks,  occur  south  of 
Oodnadatta,  and  as  isolated  hills  and  low  ranges  to  the  west  of  the 
great  valley  of  South  Australia.  Of  these,  the  chief  may  be  said  to  be 
constituted  by  the  Gawler  Range,  and  among  the  isolated  hills,  those 
at  Tarcoola  and  Wynbring.  In  addition,  portions  of  the  Flinders 
Mountains,  including  parts  of  Mount  Lofty  Ranges  near  Adelaide, 
belong  to  the  ancient  pre-Cambrian  mountain  system.  In  the  region 
west  of  the  great  valley  the  elevations  of  such  rocks  are  for  the 
most  part  inconsiderable.  It  is  the  waste  of  the  ancient  granitic 
rocks,  which,  according  to  Howchin  (1909:67),  has  supplied  the  sand 
in  the  region  to  the  north  of  the  Great  Bight.  The  elevation  of  the 
ranges  referred  to  as  being  in  the  northwestern  portion  of  the  state  is 
very  considerable,  reaching  an  altitude  of  5,200  feet,  which  is  the  great- 
est altitude  in  South  Australia. 

But  the  greatest  area  of  highlands  in  South  Australia  is  made  up  of  a 
hilly  or  mountainous  central  region  which  extends  from  the  southern 
ocean  due  north  to  Maree  (Hergott  Springs),  approximately  500  miles. 
This  elevated  region  may  perhaps  be  regarded  as  a  peneplain  which 
has  become  much  worn  down  and  much  dissected  by  streams.  It  con- 
stitutes one  geographical  unit.  In  the  northern  portions  the  mountains 
bear  the  stamp  of  an  arid  climate,  but  in  the  south  the  outlines  are 
rounded  from  the  accumulation  of  soil  and  are  well  covered  with  vege- 
tation. 

Following  Howchin,  we  can  for  convenience  separate  the  Central 
Highlands  into  three  groups.  Of  these,  the  southernmost  is  made  up 
very  largely  of  the  ranges  which  together  constitute  the  Mount  Lofty 
system.  These  attain  an  extreme  altitude  of  2,334  feet  (Mount  Lofty). 
The  middle  section  is  made  up  of  peneplains  and  rugged  hills,  the  highest 
of  which  (Mount  Bryan)  is  3,065  feet.  The  general  direction  of  the 
mountains  of  the  Central  Highlands  is  north-south.  They  are  separated 
from  one  another  by  the  undulating  plains,  peneplains,  which,  in  the 
middle  section,  along  the  line  of  the  railway  at  least,  do  not  attain  a 
greater  altitude  than  2,000  feet  above  the  sea  (Howchin  and  Gregory, 
/.  c,  86).  The  middle  section  joins  the  southern  end  of  the  Flinders 
Mountains.  Extending  as  it  does  north  to  Maree  (Hergott  Springs) 
and  east  to  Lake  Fromme,  the  FHnders  Range  constitutes  by  far  the 
largest  portion  of  the  Central  Highlands.  In  the  region  of  Port  Au- 
gusta-Quorn  the  mountains  attain  an  altitude  of  3,174  feet  (Mount 
Remarkable),  with  Mount  Brown  and  Devil's  Peak,  near  Quorn, 
slightly  less.  Mount  Arden,  about  10  miles  north  of  Quorn,  is  one  of 
the  lower  summits. 

On  its  way  north  the  railway  parallels  the  eastern  shore  of  Lake  Tor- 


38  PLANT    HABITS   AND    HABITATS    IN   THE 

rens,  and  for  much  of  the  way  skirts  the  western  base  of  the  FHnders. 
As  seen  from  the  railway  line,  the  mountains  rise  fairly  abruptly  from 
the  plain.  This  is  due,  according  to  Howchin,  to  faulting  connected 
with  the  formation  of  the  great  central  valley  of  South  Australia. 
Near  Beltana  the  line  enters  the  hills  and  at  Copley  (Leigh's  Creek)  it 
runs  in  the  valley  separating  the  smaller  western  range  from  the  main 
ranges  to  the  east.  The  highest  altitude  given  by  Howchin  of  the 
northern  Flinders  is  3,120  feet  (Freeling  Heights),  and  among  the 
prominent  elevations  is  Mount  Serle,  east  of  Copley,  to  which  refer- 
ence will  be  made  later.  It  has  already  been  mentioned  that  in  the 
north  the  Central  Highlands  assume  the  rugged  appearance  character- 
istic of  mountains  in  an  arid  land.  This  implies  also  the  presence  of 
canyons  cut  deep  by  water-courses.  Such  stream-beds  are  dry,  how- 
ever, a  large  part  of  the  year. 

For  the  most  part  the  Central  Highlands  are  of  lower  Paleozoic 
(Cambrian)  age.  The  exceptions  to  this  have  already  been  referred  to. 
There  are  occasional  structures  which  are  of  great  interest  to  the  geolo- 
gist, as,  for  example,  the  circumclinal  fault  known  as  Wilpena  Pound, 
where  a  great  basin  was  formed,  access  to  which  can  be  had  at  one 
point  only,  and  the  glacial  "till,"  supposedly  pre-Cambrian,  which  can 
be  seen  at  Depot  Flat,  near  Quorn,  as  well  as  at  other  places. 

From  the  present  standpoint  the  leading  interest  in  the  highlands  of 
South  Australia  lies  in  their  effect  on  the  climate.  The  isohyets 
and  isotherms  are  pushed  considerably  northward  by  the  central 
land  elevations  and  with  this,  and  because  of  it,  an  extra-regional 
distribution  of  plants  occurs  by  which  those  of  the  cooler  and  more 
moist  south  are  projected  far  north,  into  the  midst  of  a  region  that  is 
remarkably  hot  and  dry. 

The  lowlands  of  South  Australia  may  be  said  to  consist  mainly  of 
the  basins,  great  and  small,  in  which  the  lakes  in  the  northern  portion 
of  the  state  more  especially  are  situated,  and,  in  addition,  the  region 
along  the  course  of  the  Murray  River.  They  are  the  Lake  Eyre  Basin, 
that  of  Lake  Fromme,  Lake  Torrens,  and  Lake  Gairdner.  In  addi- 
tion are  the  coastal  plains,  of  which  the  one  between  Port  Augusta  and 
Port  Pirie  needs  only  be  mentioned.  The  positions  of  these  basins 
are  given  in  figure  10. 

The  Lake  Eyre  Basin  is  a  part  of  the  great  artesian  basin  of  central 
Australia,  which  is  estimated  by  Taylor  (1914:108)  to  have  an  area  of 
676,000  square  miles.  Only  a  relatively  small  proportion  of  the  total, 
however,  is  in  South  Australia.  The  deepest  portion  of  the  basin 
centers  in  Lake  Eyre,  the  bottom  of  which  is  estimated  to  be  60  feet 
below  the  level  of  the  sea.  Where  the  railway  crosses  the  southern 
extremity  of  the  lake  the  altitude  is  3  feet  below  the  sea.  The  basin 
is  a  closed  one,  but  the  evaporation-rate  is  so  great  that  much  of  the 
area  which  constitutes  the  lake  is  dry  most  of  the  time,  being  covered  by 


ARID    PORTIONS   OF    SOUTH    AUSTRALIA.  39 

water  only  at  times  of  flood.  In  the  south  arm,  however,  the  lake 
usually  contains  salt  water.  Important  streams  enter  Lake  Eyre  on 
the  east,  west,  and  north,  of  which  the  Barcoo,  or  Cooper's  Creek,  is  the 
most  important.  On  the  western  side  is  Neales  River,  near  which 
Oodnadatta  is  situated,  and  which  is  in  part  a  broad  and  poorly  defined 
drainage  channel,  which  carries  water  but  rarely. 

Howchin  remarks  that  the  opinion  formerly  held,  that  the  sea  had 
but  lately  retired  from  this  vast  country,  is  not  correct.  Rather  at 
a  remote  time,  the  Cretaceous,  the  sea  extended  from  the  north  as  a 
great  gulf,  or  sea,  and  covered  most  of  central  Australia.  Probably 
there  never  was  a  continuous  connection,  north  to  south,  between 
what  is  now  Spencer  Gulf  and  the  Gulf  of  Carpentaria.  The  lowest 
portion  of  the  land  connection  between  the  two  is  at  present  given 
as  being  175  feet  above  the  sea.  The  depression  in  the  southern 
portion  of  the  Great  Basin  is  thought  to  have  been  brought  about 
through  a  secondary  subsidence  affecting  this  portion  only.  The 
desert  sandstone,  as  remarked  above,  was  laid  down  in  Upper 
Cretaceous  time,  during  a  period  of  elevation  when  the  basin  was  a 
fresh-water  lake.  At  this  time  the  rainfall  was  probably  better  than 
now  and  the  climate  cooler. 

The  surface  features  of  the  Lake  Eyre  Basin,  and  these  are  repre- 
sentative of  the  entire  region,  are  of  three  kinds,  according  to  Howchin 
and  Gregory.  These  are  tablelands,  which,  as  seen  in  the  vicinity  of 
Oodnadatta,  are  generally  of  relatively  small  extent:  (1)  "buttes"  in 
fact,  (2)  stony  deserts  which  are  constituted  by  the  "gibber"  plains,  and 
(3)  the  sandhills.  At  Oodnadatta,  also,  the  surface  (except  the  tops  of 
the  buttes)  is  covered  by  small  stones  of  various  sizes  and  shapes.  The 
''gibbers"  are  usually  flattened,  polished,  and  of  a  reddish-brown  color. 
From  the  fact  that  the  stone?  fit  together  closely,  they  are  probably 
important  in  consei'ving  whatever  water  may  fall  by  cutting  down 
evaporation  from  the  surface  of  the  soil.  Just  about  Lake  Eyre,  on  all 
sides,  sandhills  are  plentiful;  in  general,  these  constitute  an  important 
feature  of  the  surface  topography  in  the  northern  part  of  South 
Australia.  The  sandhills  occur  as  ridges,  usually  not  of  great  height, 
and  run  in  a  generally  northeast  and  southwest  direction.  They  are 
frequently  separated  by  "clay-pans,"  a  quarter  of  a  mile  or  more  in 
diameter,  which  hold  water  for  a  period  after  rains.  Like  the  "gib- 
bers," the  sand  is  derived  from  the  eroded  desert  sandstone.  As 
Howchin  points  out,  owing  to  there  being  no  opportunity  for  carry- 
ing away  the  sand,  as  by  water-currents  of  whatever  kind,  it  remains 
in  the  basin,  di  if  ting  here  and  there  through  the  action  of  winds,  and 
"with  the  ever-accumulating  products  of  waste,  the  highest  hills  are 
gradually  covered  by  drift  and  the  country  is  ultimately  buried  under 
its  own  ruins"  (Howchin  and  Gregory,  1909:103). 


40  PLANT   HABITS    AND    HABITATS    IN   THE 

A  striking  and  characteristic  feature  of  the  Lake  Eyre  Basin  as  a 
whole  is  the  fact  that  it  is  an  important  part  of  the  vast  artesian  basin 
of  Austraha,  of  which  approximately  one-fifth  lies  in  South  Australia. 
There  are  numerous  "mound"  springs  on  the  border  of  Lake  Eyre 
and  many  deep  borings  have  been  made,  some  of  which  yield  great 
quantities  of  water.  The  one  at  Coward  Springs,  for  example,  has  a 
daily  flow  of  1,000,000  gallons.  The  water-supply  is  derived  from  the 
western  flanks  of  the  mountains  of  New  South  Wales  and  Queensland 
and  the  intake  is  chiefly  porous  sandstones,  probably  of  different  geo- 
logical ages.  These  sandstones  are  covered  by  great  thicknesses  of 
dark-blue  shale,  sandstones,  and  impure  limestones  of  Cretaceous  age. 
Thus  the  subterranean  water  is  far  too  deep  to  be  of  direct  benefit  to 
surface  plants,  if  it  were  always  of  suitable  quality,  which  is  sometimes 
not  the  case. 

To  the  southeast  of  Lake  Eyre  is  situated  a  chain  of  lakes,  of  which 
Lake  Fromme  is  the  largest.  These  are  described  by  Howchin  as 
being  merely  extensive  fiats  which  are  sheets  of  water  after  heavy  rains 
and  are  saline  wastes  during  dry  seasons.  They  are  the  centers  of  a 
relatively  restricted  drainage  area,  and  no  rivers  of  importance  dis- 
charge into  them. 

Another  group  of  related  basins,  somewhat  larger  than  those  of  the 
Fromme  group,  lies  to  the  west  of  Lake  Torrens  and  north  of  the 
Gawler  Ranges.  Of  these,  the  largest  is  Lake  Gairdner.  The  Trans- 
Australian  Railway  skirts  the  northern  portion  of  these  basins. 
Tarcoola  is  a  few  miles  west  of  them  and  Port  Augusta  is  50  miles,  more 
or  less,  to  the  east.  Lake  Gairdner  and  the  rest  of  the  basins  lie  at  the 
northeastern  side  of  scattered  remains  of  mountains  of  Archaean  age, 
from  the  waste  of  which  the  sand  of  the  region  may  have  been  derived. 
The  region  is  relatively  very  dry.  The  10-inch  isohyet  which,  in 
passing  through  the  Flinders  Mountains,  curves  rapidly  to  the  north, 
is  here  deflected  as  strongly  to  the  south  and  includes  none  of  the  area. 

The  northern  section  of  the  Flinders  Mountains  has  on  the  west  the 
central  rift-valley  of  South  Australia,  which  is  made  up  of  Lake 
Torrens  on  the  north  and  a  descending  series  of  flats  and  lagoons  which 
connects  it  on  the  south  with  Spencer's  Gulf.  Thus  Lake  Torrens, 
which  owes  its  existence  to  faulting,  is  in  a  manner  distinct  in  origin 
from  the  other  basins.  The  bold  western  side  of  the  Flinders  Mountains 
has  already  been  noted.  This  is  the  upthrow  side  of  the  north-south 
fault  by  which  the  Great  Valley  of  South  Australia  was  formed.  This 
fault,  as  Howchin  states,  increases  in  importance  as  it  goes  south  and 
includes  Gulfs  Spencer  and  St.  Vincent  (see  also  Taylor,  1918:97). 
The  area  of  depression,  therefore,  fairly  parallels  the  western  side  of  the 
entire  central  mountain  system  of  South  Australia. 

That  the  earth's  crust  in  this  region  is  not  in  equilibrium  is  further 
evidenced  by  the  occurrence  of  earthquakes  from  time  to  time  center- 


ARID   PORTIONS   O:^   SOUTH   AUSTRALIA.  41 

ing  along  some  portion  of  the  rift  valley.  No  important  rivers  empty 
into  Lake  Torrens  and  what  water  it  holds  is  derived  directly  from 
such  rains  as  fall  on  its  surface.  It  is  well  without  the  10-inch  isohyet, 
the  average  rainfall  of  the  basin  being  probably  but  little  over  6  inches. 

Figure  13  (Taylor,  I.  c.)  gives  concisely  the  main  points  in  the  geo- 
logical history  of  the  rift  valley  of  the  central  portion  of  the  state. 
As  Taylor  explains,  in  "A"  is  given  a  hypothetical  diagram  showing 
how  in  former  ages  there  was  a  well-developed  and  centrally  situated 
drainage  system  which  led  from  the  Barkly  tableland  on  the  north  down 
to  Jeffrey's  Deep.  The  general  course  of  the  valleys  is  north  and  south. 
The  Central  Highlands,  comprised  by  the  Flinders  and  adjoining 
ranges,  have  not  yet  been  formed.  In  "B"  important  alterations  are 
seen  to  have  taken  place.  The  sea  has  encroached  on  the  land  to  the 
south,  advancing  up  the  basin  of  the  Murray  River.  In  the  mean- 
time, epeirogenic  movements  have  raised  an  elongated  plateau  in  the 
south,  and  this  has  affected  all  of  the  river  courses,  in  places  blocking 
them  and  bringing  about  the  formation  of  lakes.  We  thus  see  the 
origin  of  all  of  the  leading  lakes  and  basins.  In  "C"  the  western  por- 
tion of  the  uplift  is  seen  to  have  slipped  in,  forming  Spencer's  Gulf  and 
Gulf  St.  Vincent.  The  MacDonnell  Ranges  (Northern  Territory) 
have  arisen  and  the  Lake  Eyre  Basin  has  sunk  away  from  the  earlier 
grade.  The  early  river  system  may  possibly  date  back  as  far  as  the 
Cretaceous,  when  a  vast  sea  covered  the  western  portion  of  Queensland. 
It  seems  certain  that  in  the  early  geologic  times  the  rainfall  was  heavy 
in  central  and  northern  South  Australia  and  in  central  Australia. 
Taylor  suggests  that  the  heavy  rainfall  in  the  past  may  have  been 
due  to  the  presence  of  great  arms  of  the  sea  to  the  east,  such  as  the 
Tertiary  sea  at  the  mouth  of  the  Murray. 

The  Murray-Darling  lowlands  are  very  extensive.  Taylor  esti- 
mates the  area  to  be  an  approximate  square  of  about  400  miles  on 
each  side.  Of  these  only  a  small  portion  is  included  within  the  state 
of  South  Australia,  and  it  is  wholly  comprised  of  the  ancient  Murray 
estuary  or  bay,  into  which,  in  earlier  geologic  times,  the  Darling  and  the 
Murrumbdigee,  as  well  as  the  Murray,  emptied  by  separate  mouths. 
The  ancient  estuary  is  for  the  most  part  flat,  except  an  area  in  the 
southeast,  where  there  are  sandhills  only  a  few  feet  above  the  sea. 
According  to  Howchin,  for  example,  at  the  point  where  the  River 
Murray  enters  the  state,  its  summer  level  is  but  57  feet  above  sea-level. 
At  Morgan  it  is  only  5  feet  4  inches,  which  gives  a  gradient  of  the  river 
of  only  0.5  inch  to  the  mile.  The  banks  of  the  river  at  Blanchtown 
are  approximately  150  feet  higher  than  the  level  cf  the  stream  at 
low  water.  As  one  overlooks  the  area  from  the  mountains  to  the 
west,  where  the  view  is  very  extensive,  it  is  unrelieved  by  any  eminences 
whatever.  This  flatness,  together  with  the  blueness  of  the  distant  mallee 
forests,  gives  the  impression  that  one  is  looking  over  the  sea. 


42  PLANT   HABITS   AND   HABITATS   IN   THE 

The  most  interesting  feature  of  the  country  is  the  River  Murray. 
The  Murray  and  its  tributaries  drain  the  western  slopes  of  mountainous 
eastern  and  central  Queensland,  New  South  Wales,  and  Victoria.  In 
favorable  seasons,  with  its  main  tributary,  the  Darling,  it  can  be 
navigated  for  2,000  miles.  At  Blanchtown  at  high-water  (as  in 
October  1918)  the  river  is  approximately  600  feet  wide.  The  vertical 
variation  between  the  summer  level  of  the  river  and  the  winter-flood 
level  is  20  feet  or  more.  In  the  area  considered  it  does  not  overflow 
its  banks  and  it  has  no  direct  and  immediate  effect  on  the  native  flora 
along  its  shores. 

CLIMATE. 

Temperature. 

South  Australia  enjoys  a  mild  temperate  climate.  The  lowest 
temperature  recorded  up  to  1912  was  at  Mount  Barker,  24.3°  F., 
and  the  highest  recorded  shade  temperature  was  119°  F.  at  William 
Creek,  in  the  far  north,  about  midway  between  Maree  (Hergott  Springs) 
and  Oodnadatta.  The  former  is  near  the  southern  termination  of  the 
Central  Highlands  and  the  latter  is  in  the  Lake  Eyre  Basin.  Except 
in  the  more  arid  districts  the  seasonal  and  the  diurnal  variations  are 
not  extreme. 

The  65°  F.  isotherm  enters  the  state  slightly  south  of  the  center  of  the 
eastern  border,  curves  to  the  north  in  crossing  the  Central  Highlands, 
dips  south  in  the  Lake  Gairdner  Basin,  and,  taking  a  northwestern 
direction,  reaches  the  highlands  in  the  extreme  northwestern  portion 
of  the  state.  Here  it  is  again  deflected  sharply  north  and  leaves  the 
state  not  far  from  the  northwestern  corner.  About  64  per  cent  of  the 
entire  area  of  South  Australia  is  within  the  65°  to  75°  F.  isotherms. 

The  really  great  difference  in  the  apparent  amount  of  heat  received 
by  the  northern  and  mainly  arid  (as  contrasted  to  the  southern  and 
mainly  humid)  portions  of  the  state  is  further  suggested  by  the  number 
of  days  in  each  in  which  the  thermometer  registers  a  shade  temperature 
of  90°  F.  or  more.  At  William  Creek,  for  example,  there  are  on  the 
average  114  days  in  each  year  when  the  thermometer  registers  a 
temperature  of  90°  F.  or  over,  while,  on  the  other  hand,  at  Adelaide, 
which  is  by  no  means  the  coolest  southern  station,  the  number  of 
days  in  which  the  thermometer  shows  this  temperature  is  only  43  in 
the  year.  This  may  not  mean,  however,  that  there  is  a  corresponding 
difference  in  the  amount  of  heat  units  actually  received  between  the 
two  stations,  since  there  are  nearly  three  times  as  many  nights,  40  as 
against  14,  during  which  the  thermometer  records  a  temperature  of 
40°  F.  or  less  at  WiUiam  Creek,  as  opposed  to  night  temperature  at 
Adelaide.  Here  again  the  temperature  at  Adelaide  probably  does 
not  represent  the  extreme  condition,  but  reveals  the  steadying  in- 
fluence of  the  Southern  Ocean,  near  which  the  city  is  situated. 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  43 

The  main  influences  which  shape  the  temperature  of  South  Australia 
are  the  latitude,  the  relation  of  the  state  to  the  balance  of  the  continent 
and  to  the  Southern  Ocean,  and  the  topographical  variation  of  the 
state  itself. 

The  temperature  conditions  of  the  Lake  Eyre  Basin,  of  the  Flinders 
Ranges,  and  of  the  southern  end  of  the  central  rift  valley  will  be  char- 
acterized in  connection  with  descriptions  of  the  flora  of  these  respective 
regions.  In  this  place  it  will  be  necessary  only  to  refer  to  the  tempera- 
ture of  the  plateau  region  of  the  western  portion  of  the  state. 

As  described  in  the  preceding  section,  the  Western  Plateau  is  a  vast 
region,  since  it  is  united  to  the  plateau  of  Western  Australia.  The 
extreme  north-south  extent  is  approximately  700  miles.  Not  much 
is  known  exactly  in  regard  to  the  meteorological  conditions  of  most  of 
the  plateau.  The  reason  for  this  lies  in  its  sparse  settlement  and  in 
the  fact  that  much  of  it  is  hardly  more  than  explored.  From  the 
usually  meager  notes  of  the  rare  explorer,  however,  it  is  known  that  in 
the  northern  and  western  portions  of  the  plateau  there  is  a  very  con- 
siderable daily  as  well  as  large  seasonal  variation  in  temperature. 

Howchin  and  Gregory  (1909:145)  state  that  in  the  inland  and  central 
regions  the  diurnal  variation  may  be  as  great  as  40°  to  50°  F.,  and  that 
in  winter,  while  the  days  may  be  very  warm,  the  cold  at  night  may  be 
sufficiently  intense  to  freeze  the  contents  of  a  water-bag  into  a  solid 
mass  of  ice.  The  same  authors  cite  the  observations  made  on  tem- 
perature by  the  Elder  Scientific  Exploring  Expedition,  1891-92,  which 
crossed  the  plateau  between  the  Peake  and  Western  Australia  borders. 
In  winter  during  the  day  the  temperature  was  about  60°  to  80°  F.,  but 
at  night  it  dropped  to  8°  or  10°  below  freezing.  White  (1915:713), 
speaking  of  the  northern  portion  of  the  plateau,  says  that  just  before 
reaching  the  foothills  of  the  Musgraves  camp  was  made  in  a  dense 
thicket — ''the  night  was  bitterly  cold  and  everything  was  frozen  hard." 

Further  south  the  temperature,  especially  of  summer,  is  greatly 
influenced  by  the  Great  Bight  to  the  south.  In  an  earlier  account  of 
the  general  temperature  conditions  of  the  continent  reference  has 
already  been  made  to  the  drying  effects  of  the  desert  winds,  and  it  was 
stated  that  these  effects  are  to  be  experienced  several  hundred  miles 
from  the  deserts  themselves.  In  the  southern  portion  of  the  Great 
Plateau  region,  however,  opposite  conditions  may  also  be  encountered. 
For  example,  at  Tarcoola,  which  is  100  miles  or  more  from  the  Bight, 
its  influence  is  frequently  met.  The  summer  temperatures  at  the  place 
may  be  as  high  as  118°  F.,  as  unofficially  reported,  but  after  a  wind 
from  the  south  sets  in  the  drop  in  temperature  is  immediate  and 
considerable.  It  may  be  remarked  that  similarly  situated  regions 
of  the  state  also  share  the  cooling  effects  of  the  winds  from  off  the 
southern  sea. 


44 


PLANT   HABITS   AND   HABITATS   IN   THE 


Rainfall. 

South  Australia  is  the  only  state  of  the  Commonwealth  in  which  the 
area  receiving  10  inches,  or  less,  of  rain  is  greater  than  the  area  which 
receives  more  than  10  inches.  The  ratio  of  the  two  is  roughly  6:1. 
The  10-inch  isohyet  runs  in  a  general  east-west  direction.  The  15-inch 
isohyet  lying  to  the  south  has  a  fairly  similar  course,  but  the  northern- 
most point  attained  is  at  the  southern  end  of  the  Flinders  Mountains, 
near  Mount  Remarkable.  Between  these  two  isohyets  lies  ''Goyder's 
Une  of  rainfall,"  which  marks  the  northern  limit  for  the  successful 
growing  of  wheat.  The  pastoral  occupations  are  mainly  carried  on  in 
the  country  of  intermediate  rainfall  to  the  north  of  "Goyder's  line," 
although  sheep  in  large  numbers  are  raised  in  the  far  north.  The 
leading  industries  of  the  state  can  thus  be  said  to  be  strictly  limited  and 
made  possible  by  the  amount  and  the  distribution  of  the  rain. 

Table  10. — Rainfall  of  1  inch  or  more  occurring  in  S4  hours  at  Oodnadatta,  Copley,  and 
Quorn,  1901-1906. 


Year. 

Oodnadatta. 

Copley. 

Quorn. 

Date. 

Amount 

in 
inches. 

Total 

for 
year. 

Date. 

Amount 

in 
inches. 

Total 
for 
year. 

Date. 

Amount 

in 
inches. 

Total 

for 
year. 

1901 

1902  .    . 

Feb.  20 

1.67 

none, 
none. 

1.82 

1.68 

1.26 

none. 

4.94 

2.61 
5.43 

8.92 

5.69 
3.03 

Feb.   12 
Aug.  25 

1.31 
1.20 
none. 
1.26 
3.20 

none. 

none. 
2.89 
1.75 
1.10 

6.49 

1.95 
11.53 

9.76 

5.03 
13.00 

none. 

none. 
1.09 
1.27 
1.43 
1.84 

3.10 
1.57 
1.12 
1.32 
1.45 

10.14 

7.76 
18.09 

13.09 

12.82 
18.74 

1903   . 

Nov.  27 
Dec.  28 

Sept.  17 
Oct.    17 
Oct.   26 
Feb.   19 

May    8 
June  11 
June  22 
Sept.  27 
Nov.  14 

1904 

1905 

1906 

Feb.  19 
Feb.  26 
Jan.    28 

May  23 
June  18 
Sept.  17 

The  rainfall  of  South  AustraUa  is  periodic.  The  seasons  of  rainfall 
are  the  best  marked  in  the  southern  portion.  As  one  progresses  north- 
ward the  distribution  through  the  year  is  more  equable  until  the  far 
north  is  reached,  when  the  rainfall  conditions  typical  of  the  central 
portion  of  the  continent  are  met.  Thus  at  Adelaide,  which  may  be 
used  to  illustrate  the  rainfall  conditions  of  the  southern  districts,  about 
80  per  cent  of  the  rain  occurs  during  the  cool  season.  The  average 
rainfall  at  Adelaide  is  21.06  inches.  At  Quorn,  near  the  southern  end 
of  the  Flinders  Ranges  and  nearly  midway  in  the  Central  Highlands 
section  of  the  state,  the  average  yearly  rainfall  is  13.82  inches.  Of 
this,  about  57  per  cent  occurs  in  the  cool  season.  At  Copley,  near  the 
northern  end  of  the  Flinders  and  on  the  western  side  of  the  mountains, 
the  amount  of  rainfall  in  the  cool  season,  April  to  August,  is  about  38 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


45 


per  cent  of  the  total  for  the  year.  The  average  rainfall  at  Copley  is 
about  8.7  inches.  At  Oodnadatta,  where  the  rainfall  is  4.85  inches,  the 
percentage  falling  in  the  months  mentioned  is  about  the  same  as  at 
Copley. 

The  periodic  rainfall  in  the  southern  and  central  portions  of  South 
Australia  and  the  more  equable  distribution  in  the  north  are  directly 
related  to  the  seasonal  north-south  shifting  of  the  climatic  complex. 


1903         1905 
1902        1904        t906 


1903        1905 
1902         1904        1906 


1901         1903         1905 

1902         1904         1906 


Fio.  11. — Grapha  showing  the  annual  (total)  and  "non-effective"  rainfall  for  1901-1906  at 
Oodnadatta  (a),  Copley  (b),  and  Quorn  (c),  South  Australia,  based  on  recordi 
supplied  by  the  Adelaide  office  of  the  Commonwealth  Bureau  of  Meteorology. 

As  Taylor  graphically  shows  (1918:  Solar  control  model),  the  pre- 
vailing Une  of  the  center  of  high  pressures  in  mid-winter  coincides 
nearly  with  the  northern  boundary  of  South  Australia,  but  in  midsum- 
mer it  is  far  south  of  the  state.  The  prevailing  winds  in  summer, 
therefore,  are  from  the  east,  or  southeast,  and  are  drying  winds.  But 
at  this  time  occasional  lows  from  the  northern  part  of  the  continent 
may  extend  far  to  the  south,  reaching  the  northern  part  of  South 
Australia,  bringing  rain.  In  winter,  however,  the  center  of  highs,  as 
before  remarked,  crosses  the  extreme  north  of  the  state,  the  belt  of 
westerlies  touches  the  extreme  south,  and  a  belt  of  variabes  lies  be- 
tween.   The  dry  easterlies  are  now  far  to  the  north,  and  rain  occurs  in 


46  PLANT   HABITS   AND   HABITATS   IN   THE 

the  south.  The  storms  of  winter  are  cyclonic  in  character.  Areas  of 
low  pressure  (cyclonic)  alternate  with  areas  of  high  pressure  (anti- 
cyclonic.)  The  former  are  ascending,  expandmg  currents  and  therefore 
deposit  their  moisture;  the  latter  are  descending,  condensing  currents, 
cold  and  therefore  dry. 

From  this  it  will  be  seen  that  the  rains  in  the  southern  portion  of 
South  Australia  and  in  the  highlands  extending  north  into  the  center  of 
the  state,  which  project  the  southern  climatic  conditions  to  the  north, 
are  periodic  and  also  dependable.  But  the  rains  of  the  northern  poi  tion 
of  the  state  are  not  regularly  controlled  by  the  winter  climatic  con- 
ditions, or  those  of  summer,  and  hence  are  not  dependable  and  are 
scarcely  periodic.  Further,  as  indicated  in  an  earlier  paragraph,  the 
midstate  region  has  a  rainfall  of  an  intermediate  character,  both  as 
regards  the  amount  and  as  regards  the  periodicity. 

The  lowest  rainfall  reported  in  South  Australia  is  at  Kanowana, 
Lake  Eyre  Basin,  where  it  is  4.33  inches,  the  average  of  observations 
covering  a  period  of  18  years.  The  rainfall  in  all  of  the  basins  is  low, 
and  that  of  the  Murray,  although  of  larger  amount  than  the  others, 
is  nevertheless  relatively  low.  This  may  be  because  of  the  proximity 
of  highlands  to  the  west.  Lake  Eyre  is  in  the  midst  of  the  5-inch 
isohyet.  The  basins  of  Lake  Torrens,  Lake  Gairdner,  and  Lake 
Fromme  have  about  2  or  3  inches  more  rainfall  than  that  of  Lake  Eyre. 

Over  a  very  considerable  area  in  the  drier  portions  of  the  state  the 
rainfall  is  to  a  very  considerable  degree  uncertain  as  to  amount. 
This  is  true  both  as  regards  that  for  the  entire  year  and  for  separate 
storms.  Thus,  it  will  be  shown  below  that  a  relatively  large  percentage 
of  the  precipitation  in  the  northern  parts  of  South  Australia  occurs  in 
amounts  too  small  to  directly  benefit  plants.  But,  on  the  other  hand, 
a  very  large  portion  of  the  yearly  rainfall  sometimes  occurs  in  a  single 
storm.  In  the  latter  instance  much  of  the  precipitation  does  not  pen- 
etrate the  ground,  but  runs  off  and  does  not  benefit  plants  directly. 
In  the  latter  rain-type  it  is  difficult  to  estimate  the  proportion  which 
can  be  said  to  be  effective,  since  it  depends  on  the  nature  of  the  soil, 
the  plant  cover,  and  (not  to  mention  other  features)  the  slant  of  the 
surface,  as  well  as  the  character  of  the  storm  itself.  For  these  reasons 
only  the  smaller  precipitation  amounts,  as  presented  in  the  follow- 
ing section,  are  deducted  from  the  entire  rainfall  in  order  to  arrive  at 
the  amount  of  rainfall  which  can  be  said  to  be  "effective." 

It  will  be  seen  in  table  10  that  about  25  per  cent  of  the  yearly  rainfall 
may  occur  in  a  single  storm,  for  example  that  of  May  8,  1905,  at 
Quorn.  And  at  Oodnadatta,  in  1901,  the  relative  amount  was  even 
greater,  although  the  actual  precipitation  in  the  single  large  storm  of 
the  year  was  less.  The  greatest  single  rain  recorded  at  the  three  sta- 
tions given  in  the  table  and  for  the  years  referred  to  was  on  December 
28,  1903,  at  Copley,  when  3.20  inches  were  reported. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  47 

Effective  Rainfall. 

It  does  not  require  long  experience  with  the  chmate  of  South  Austra- 
Ua,  particularly  with  the  drier  portions  of  the  state,  to  recognize  the 
probability  that  not  all  of  the  rainfall  reported  in  the  official  summaries 
is  of  direct  benefit  to  the  native  flora.  Also,  what  may  be  said  to  be  an 
effective  rainfall,  from  this  point  of  view,  at  one  period  of  the  year 
may  not  be  so  at  another  period.  And,  further,  the  time  relations  of 
successive  storms  must  also  be  considered. 

In  order  to  determine  what  might  be  considered  a  minimum  rainfall 
for  the  native  plants,  the  actual  penetration  following  rains  of  known 
but  small  amounts  was  observed  and  measured  on  a  few  occasions. 
Thus,  at  Copley,  on  a  morning  following  a  slow  rain  amounting  to 
0.21  inch,  it  was  found  that  the  ground  was  freshly  moistened  to  a 
depth  of  4  to  9  cm.  At  another  time,  when  a  rainfall  of  0.27  inch  was 
reported,  the  soil  was  found  wetted  to  a  depth  of  5  to  8.5  cm.  The 
last  observations  were  made  4  hours  after  the  rain  had  ceased  falling. 

On  the  plain  near  Copley  there  are  numerous  diminutive  drainage 
channels,  15  cm.  deep,  or  less.  These  may  form  separate  systems  of 
considerable  extent,  or  they  may  be  tributary  to  larger  drainage  sys- 
tems. Whichever  it  might  be,  it  was  noticed  that  in  none  of  the  small 
channels  were  there  pools  following  a  rain  of  0.27  inch.  The  rain 
penetrated  where  it  fell.  At  Ooldea,  also,  after  a  rainfall  amounting 
to  0.21  inch,  the  soil  was  found  to  have  been  moistened  to  a  depth  not 
exceeding  3.5  cm.  In  both  situations  there  was  a  large  percentage 
of  sand  in  the  soil. 

As  will  be  shown  in  another  place,  the  depths  given  would  include 
the  horizon  within  which  the  roots  of  many  winter  annuals  are  to  be 
found  and  also  the  most  superficially  placed  roots  of  certain  of  the 
perennials.  Deeply  rooted  plants  of  all  sorts  would  not  benefit 
directly  by  falls  of  rain  of  these  amounts;  and  it  may  be  questioned 
whether  in  summer  such  small  rains  would  benefit  the  annuals  or  the 
superficially  rooted  perennials,  owing  to  the  rapid  evaporation  from 
the  surface  of  the  soil.  The  foregoing  remarks  have  been  made  with 
respect  to  individual  storms. 

If  separate  storms  follow  one  another  with  little  time  intervening, 
it  is  clear  that  there  would  be  a  progressive  moistening  of  the  soil,  with 
the  effect  that  the  total  depth  moistened  might  be  considerable.  It  is 
necessary,  therefore,  to  take  into  account  the  time  which  elapses  be- 
tween successive  stormy  periods.  However  discouraging  for  exact 
statement  such  considerations,  and  others  that  will  readily  occur, 
may  be,  it  seems  worth  while  to  establish  tentatively  what  may  be  con- 
sidered the  minimum  effective  rainfall.  And  before  making  the  defini- 
tion it  should  be  pointed  out  that  it  concerns  the  native  vegetation 
and  not  that  of  agricultural  value,  inasmuch  as  the  amount  in  the  latter 
case  would  necessarily  be  greater.    Musson  (1904:3)  states  that  only 


48 


PLANT   HABITS   AND   HABITATS   IN   THE 


rains  amounting  to  over  "20  points,"  i.  e.,  0.20  inch,  do  real  good  in  an 
agricultural  way.  With  these  and  other  observations  in  mind,  it  has 
been  concluded  to  lower  the  minimum  and  to  define  an  ecologically 
effective  rainfall  as  one  consisting  of  0.15  inch,  or  more,  and  which 
occurs  in  a  distinct  rainy  period.  Whether  subsequent  study  will 
establish  another  minimum  does  not  concern  us  at  present.  It  will  be 
useful,  if  for  no  other  purpose,  to  show  how  large  a  percentage  of  the 
total  annual  rainfall  in  the  dry  interior  is  of  little  or  no  moment  to  the 
native  vegetation,  and  hence  how  very  arid  the  region  really  is. 

The  effective  rainfall  for  Oodnadatta,  Copley,  and  Quorn  was  de- 
termined for  a  period  of  five  successive  years,  and  the  results  are  pre- 
sented in  table  11.  The  last  column  of  the  table  gives  also  the  actual 
recorded  rainfall  for  each  of  the  years  referred  to.     It  will  be  seen  that 


Table  11 

.—Monthly 

effective  rainfall  at  Oodnadatta,  Copley,  and  Quorn,  South  Australia, 
for  1901-1906,  in  inches. 

Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

■ 

Total 
effec- 
tive 
rain- 
fall. 

Total 
rain- 
fall. 

Oodnadatta: 

1901 

1902 

1903 

1904 

1906 

1906 

Copley: 

1901 

1902 

1903 

1904 

1905 

1906 

Quorn : 

1901 

1902 

1903 

1904 

1906 

1906 

0.0 

0.0 

0.40 

0.0 

0.0 

0.0 

0.0 
0.0 
0.0 

.26 
0.75 
0.0 

0.0 

0.0 

0.42 

0.95 

0.66 

0.0 

3.87 

0.0 

0.0 

3.01 

0.0 

O.G 

2.67 

0.0 

0.0 

0.46 

0.0 

0.65 

0.53 
0.41 
0.49 
2.45 
0.45 
0.67 

0.0 

0.0 

0.0 

0.20 

0.0 

0.0 

0.0 

0.0 

0.86 

0.0 

0.0 

1.86 

0.0 

0.96 

1.40 

0.0 

0.0 

2.09 

0.0 

0.0 

1.69 

0.0 

0.27 

0.0 

0.27 

0.0 

0.20 

0.17 

0.0 

0.0 

0.39 

0.0 

1.75 

0.30 

0.90 

0.0 

0.0 

0.0 

0.31 

0.36 

0.23 

0.64 

0.0 

0.0 

0.60 

1.21 

0.49 

3.43 

0.0 

0.0 

0.68 

0.22 

3.96 

1.53 

0.0 

0.0 

0.0 

0.20 

1.56 

0.0 

0.40 

0.0 

0.0 

0.62 

0.95 

1.75 

0.91 
1.15 
0.69 
1.17 

0.84 
4.40 

0.0 

0.50 

0.0 

0.71 

0.67 

0.17 

0.0 

0.15 

0.16 

1.75 

1.06 

0.37 

1.19 

0.0 

0.90 

1.62 

1.30 

1.14 

0.20 

0.0 

0.60 

0.0 

0.0 

0.0 

1.71 

0.0 

0.67 

0.54 

0.0 

0.60 

2.37 
0.34 
0.27 
0.54 
0.38 
0.70 

0.0 

0.0 

0.0 

2.16 

0.0 

0.60 

0.32 
0.58 
2,21 
1.08 
0.66 
1.70 

0.86 

0.59 

2.76 

0.0 

0.21 

2.61 

0.0 

0.0 

0.0 

0.65 

0.25 

0.0 

0.25 

0.0 

0.0 

1.22 

0.52 

0.15 

1.99 
1.50 
0.15 
2.99 
1.07 
0.91 

0.0 

0.65 

1.11 

0.0 

0.0 

0.0 

0.0 

0.48 

1.76 

0.15 

0.0 

0.80 

0.0 

0.0 

5.27 

0.57 

0.0 

1.72 

0.0 

0.87 

0.35 

0.0 

0.0 

0.0 

0.0 

0.0 

3.25 

1.23 

0.0 

0.80 

0.0 

0.57 

0.77 

0.34 

0.0 

0.90 

4.07 
2,02 
4.46 
7.29 
2.98 
1.31 

5.62 
1.21 
9.71 
8.69 
4.43 
12.11 

8.24 
6.52 
15.55 
11.15 
9.77 
16.47 

4.94 
2.61 
6.48 
8.92 
6.69 
3.03 

6.49 
1.95 

11.63 
9.76 
6.03 

13.00 

10.14 
7.76 
18.09 
13.09 
12.82 
18.74 

Table  12. — Mean,  highest,  and  lowest  monthly  rainfall  at  Oodnadatta,  in  inches,  for  a  period 

of  26  years. 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct, 

Nov. 

0.38 
1.41 

Dec. 

Year. 

Mean 

Highest.... 

0.71 
5.18 

0.71 
4.16 

0.57 
4.32 

0.18 
1.79 

0.23 
1.54 

0.64 

27.71 

0.28 
1.6S 

0.11 
0.60 

0.32 
2.21 

0.34 
2.03 

0.38 
1.79 

4.85 
8.92 
1.54 

H 

ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  49 

the  percentage  of  what  may  be  called  the  non-effective  rainfall  in- 
creases with  the  decrease  in  the  total  average  rainfall.  At  Quorn,  for 
example,  it  is  18  per  cent,  at  Copley  it  is  19  per  cent,  and  at  Oodnadatta 
it  is  30  per  cent  for  the  years  under  consideration.  Assuming  that 
these  figures  represent  the  average  percentage  of  the  non-effective  rain- 
fall, which  may  or  may  not  be  the  case,  and  knowing  the  actual  average 
rainfall  for  the  three  stations,  the  expected  efficient  rainfall  can  be 
easily  calculated.  For  example,  the  average  rainfall  at  Oodnadatta  is 
4.85  inches.  This  being  the  case,  a  correction  for  the  percentage  that 
does  no  good  to  the  native  vegetation  would  give  an  efficient  average 
rainfall  of  3.42  inches.  The  average  rainfall  for  Copley  is  8.70  inches, 
which  would  amount  to  7.13  inches  effective  rainfall,  and  that  at  Quorn 
is  13.72  inches.  At  the  latter  station  the  effective  amount  would  be 
11.11  inches.  The  relation  of  the  total,  the  effective  and  the  non- 
effective, rainfall  at  Oodnadatta,  Copley,  and  at  Quorn  is  shown 
graphically  in  figure  11.  In  1906  the  non-effective  rainfall  at  Oodna- 
datta was  43  per  cent  of  the  total  recorded  for  the  year.  Thus  the 
effective  amount  of  precipitation  for  the  year  at  Oodnadatta  was 
1.7  inches.  This  exceeds  the  percentage  of  non-effective  rainfall  of 
each  of  the  other  stations  whose  records  were  studied  and  indicates 
(together  with  the  average  percentage  of  non-effective  rainfall  for  the 
stations  given  above)  that  the  curve  of  aridity  falls  more  rapidly, 
as  one  goes  from  a  less  to  a  more  arid  station,  than  the  curve  of  the 
rainfall  itself. 


50  PLANT   HABITS   AND   HABITATS   IN   THE 

VEGETATION  AND   PLANT   HABITATS   IN  VICINITY  OF 
OODNADATTA. 

PHYSIOGRAPHY. 

The  country  to  the  south  and  to  the  west  of  Lake  Eyre  and  Lake 
Eyre  South,  as  seen  from  the  railway,  has  a  monotonous  topography, 
although  not  without  a  certain  diversity.  As  one  goes  west  from 
Maree  (Hergott  Springs)  the  land-surface  on  every  side,  except  to  the 
south,  is  fairly  level.  Some  distance  on  the  south  lies  the  north- 
western spur  of  the  Flinders  Ranges,  but  in  the  other  directions  the 
general  fiat  expanse  is  broken  only  occasionally  by  low  hills  or  mounds. 
Maree  lies  on  the  southern  edge  of  the  great  Australian  artesian  basin 
and  in  its  vicinity,  as  elsewhere  along  the  line  of  the  railway,  mounds 
mark  the  presence  of  springs.  There  are  50  or  more  of  these  springs 
in  the  southern  and  southwestern  part  of  the  basin.  The  water  is 
charged  heavily  with  mineral  matter  and  upon  evaporation  leaves  a 
calcareous  deposit.  Thus  the  travertine  mounds  are  formed.  The 
water  flows  out  of  the  summit  of  the  mounds  and  extends  for  a  greater 
or  less  distance  from  the  base.  The  mound  springs  thus  can  carry 
vegetation  and  are  often  the  only  green  spots,  truly  oases,  on  a  parched 
and  barren  plain. 

But  the  leading  characteristic  of  the  country  to  the  south  of  Lake 
Eyre  South  is  its  flatness.  On  every  side  it  is  a  plain,  and  to  the  north 
it  stretches  as  far  as  the  eye  can  reach,  a  grayish-green  plain  that  finally 
merges  in  a  mirage,  suggesting  flat  expanses  of  a  lake.  Shortly  before 
reaching  the  station  of  Stuart's  Creek  the  railway  crosses  what  is 
probably  the  southern  edge  of  the  bed  of  the  lake  of  earlier  times, 
running  below  the  level  of  the  sea,  and  here,  on  the  rare  occasions 
when  filled  with  water,  it  may  be  seen  from  the  railroad.  Thus,  in 
July  1918,  there  seemed  to  be  water  in  the  south  arm  of  the  lake. 

After  leaving  Stuart's  Creek  the  railway  ascends  gradually  until 
at  Oodnadatta  it  is  about  400  feet  above  sea-level.  The  topography 
becomes  more  broken  and  presents  several  features  of  especial  interest. 
Beyond  William  Creek  some  worn-down  pre-Cambrian  hills  extend,  and 
flat-topped  hills  may  be  seen  to  the  west,  which  are  probably  outliers 
of  the  desert  sandstone  tableland  (Upper  Cretaceous).  Occasionally 
sandhills  were  seen  lying  toward  Lake  Eyre.  The  railway  line  also  runs 
among  low  hills  and  along  salt  flats,  and  finally,  not  far  south  of  Oodna- 
datta, it  crosses  a  wide  and  poorly  defined  river  bottom,  which  at  the 
time  of  my  visit  was  dry.  Thus  we  have  the  leading  topographical 
elements  of  the  Oodnadatta  region,  namely,  the  lower  plain,  itself 
somewhat  diversified,  on  which  the  railroad  runs,  the  flat-topped  hills, 
the  sand  dunes,  and  the  drainage  channels. 

Oodnadatta,  which  is  the  present  end  of  the  railway  running  from 
Adelaide,  and  approximately  700  miles  from  that  city,  is  situated  near 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  51 

the  western  edge  of  the  great  Australian  artesian  basin.  It  is  about  100 
miles  to  the  north  of  west  of  the  northern  end  of  Lake  Eyre.  The 
most  important  topographical  feature  of  the  immediate  neighborhood 
of  the  town  is  the  lower  plain  (Lower  Cretaceous)  on  which  it  is  situated. 
Outlying  members  of  the  higher  plain,  the  desert  sandstone  tableland, 
can  be  seen  to  the  westward  (plate  1a)  .  These  flat-topped  hills  are  a 
striking  feature  of  the  topography  of  the  region.  The  surface  both 
of  the  lower  and  of  the  upper  plain  is  usually  covered  with  fairly  small 
stones,  the  gibbers,  which  were  left  by  the  wind  after  all  fine  material 
had  been  removed  (plate  1b).  Although  a  superficial  view  over  the 
lower  plain  gives  the  impression  that  it  is  quite  flat,  when  seen  more 
closely  such  is  found  not  to  be  the  case.  It  is  slightly  undulating  and 
there  are  shallow  depressions,  apparently  wind-scooped,  here  and 
there,  where  gibbers  appear  to  be  wanting,  and  which  are  but  a  few 
inches  below  the  general  level  of  the  plain.  Such,  as  will  be  mentioned 
below,  are  in  fact  miniature  oases  which  support  a  characteristic 
vegetation  in  the  midst  of  a  plain  otherwise  quite  barren. 

So  far  as  I  saw,  the  surface  of  the  fliit-topped  hills,  which  are  the  re- 
mains of  the  upper  plains,  it  is  much  like  that  of  the  lower  plain, 
except  that  the  effects  of  erosion  are  more  marked.  There  are  small 
depressions  in  this  plain  also,  and  it  is  covered  with  gibbers.  Possibly, 
as  will  be  remarked  later,  the  upper  plains  constitute  the  most  arid 
habitats  of  the  great  basin. 

The  most  prominent  water-course  in  the  vicinity  of  Oodnadatta  is 
Neales  River.  At  Oodnadatta  the  river-bottoms  are  defined  by  low 
banks,  and  are  possibly  6  feet  below  the  general  level  of  the  lower  plain. 
But  as  the  river  goes  southeast  on  its  way  to  Lake  Eyre,  the  course 
widens  and  is  not  so  sharply  delimited  as  it  is  near  Oodnadatta. 
Neales  River  and  the  Macumba  River  constitute  the  only  rivers  leading 
into  Lake  Eyre  from  the  western  side  of  the  basin.  At  a  point  west  of 
Oodnadatta  and  about  a  mile  distant,  the  bottoms  of  Neales  River  are 
nearly  a  mile  across.  The  surface  of  the  bottoms,  or  flood-plain,  is 
level.  There  is  no  continuous  and  well-defined  water-course  here, 
but  at  various  places  along  the  bottoms  are  depressions,  100  meters  or 
less  in  length,  which  contain  water  after  rains.  These  depressions  have 
the  appearance  of  having  been  gouged  out  by  water  at  the  time  of  high 
floods,  which  rarely  occur.  It  is  doubtful  whether  the  water  of  the 
rivers  ever  empty  into  Lake  Eyre.  Just  north  of  Oodnadatta  there 
are  flats  which  may  possibly  drain  into  the  Neales  River;  and  several 
miles  farther  north,  as  viewed  from  the  summit  of  O'Halloran's 
Mount,  there  are  extensive  flats  also,  with  narrow  contributory  chan- 
nels, which  probably  act  as  reservoirs  for  the  reception  and  catchment 
of  flood-waters.  All  of  these  are  probably  related  to  the  drainage  of 
the  main  river. 

Besides  the  plains  and  the  drainage  channels  of  whatever  kind,  in 
connection  with  the  topographical  features  of  the  region  one  should 


52  PLANT   HABITS   AND   HABITATS   IN   THE 

also  mention  the  sandhills  and  accompanying  clay-pans  situated  2  or  3 
miles  east  and  south  of  Oodnadatta.  The  sandhills  lie  on  the  lower 
plain  and  vary  considerably  in  plan,  extent,  and  height.  The  highest 
seen  were  estimated  to  have  an  altitude  of  about  15  meters  above  the 
plain  and  to  be  about  50  meters  in  diameter.  They  are  round,  oblong, 
or  crescentic  in  plan.  The  windward  slopes  of  some  are  gradual  and 
the  lee  slopes  steep.  Ripple  marks  also  are  to  be  seen  on  most  of  the 
dunes.  From  such  features  it  is  concluded  that  not  all  of  the  sandhills 
are  fixed.  Adjoining  the  sandhills,  or  between  them,  are  clay-pans 
which  vary  greatly  in  size,  some  being  1,200  meters,  more  or  less,  in 
diameter.  The  surface  is  hard  and  glistens  in  the  sunlight.  Although 
when  seen  the  clay-pans  were  entirely  dry,  whenever  rains  occur  they 
are  covered  with  water  which  apparently  escapes,  mainly  by  evapora- 
tion, inasmuch  as  the  surface  of  the  pans  is  of  fine  texture,  apparently 
silt,  which  would  allow  but  relatively  slow  penetration. 

In  one  group  of  sandhills  the  clay-pans  appeared  to  extend  beneath 
the  dune,  although  this  was  not  surely  determined.  If  true,  it  would 
follow  that  under  such  a  condition  there  might  be  important  water 
reservoirs  in  the  sandhills  and  at  no  great  depth.  "Soaks"  among 
the  sandhills,  as  possibly  at  Ooldea,  may  have  such  an  origin  and  struc- 
ture. Howchin  (1909:103)  says  that  sandy  ridges  and  clay-pans  form 
the  southern  plains  of  the  central  portion  of  Australia  and  occur 
largely  on  the  eastern  and  northern  sides  of  Lake  Eyre,  and  points  out 
that  such  an  inland  basin  as  that  of  Lake  Eyre  can  not  get  rid  of  its 
worn-down  material,  the  product  of  erosion,  "such  as  occurs  when  the 
drainage  of  the  country  flows  into  the  sea,  whilst  from  a  deficiency  of 
moisture,  vegetation  is  scarce  and  the  soil  but  loosely  held  together. 
From  this  cause  the  soil  and  sand  are  constantly  on  the  move." 

From  the  foregoing  sketch  of  some  of  the  leading  physiological 
features  in  the  vicinity  of  Oodnadatta  it  will  be  clear  that  the  character 
of  the  soil  varies  considerably.  On  the  plains,  for  example,  it  appears 
to  be  fine  sand  with  an  admixture  of  pebbles  of  different  sizes.  The 
largest  of  these  constitute  the  "gibbers,"  or  desert  pavement,  which 
protect  the  fine  soil  beneath  from  being  carried  away  by  the  wind  and 
from  rapid  drying  out.  In  the  shallow  hollows  on  the  plains,  as  has 
already  been  alluded  to,  there  are  no  "gibbers."  This  also  is  true  on 
the  flood-plain  of  Neales  River,  where,  however,  the  small  stones  are 
largely  wanting  and  the  soil  is  relatively  sandy.  On  the  plains  the  top- 
soil  appears  to  be  about  50  cm.  deep,  and  on  the  flood-plain  it  is  2 
meters,  and  probably  much  more,  in  depth. 

In  places  on  the  plains  where  erosion  has  occurred  and  the  substratum 
is  exposed,  it  is  seen  to  be  of  a  white  color  and  often  of  considerable 
thickness.  How  generally  this  extended  was  not  learned.  From  the 
appearance  of  the  material  it  was  assumed  to  be  gypsum,  although  in 
certain  places  where  the  layer  of  material  was  thin,  as  where  it  covered 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  53 

stones,  it  may  well  be  travertine  or  desert  limestone.  The  nature  of 
the  sandhills  has  already  been  mentioned  and  need  not  be  taken  up 
further.  As  to  the  clay-pans  of  the  sandhill  neighborhood,  it  need  only 
be  said  that  in  them,  as  elsewhere  where  the  drainage  is  poor  or  lacking, 
there  is  an  excessive  accumulation  of  salts.  In  the  clay-pans  the  flood- 
ing water  is  at  first  fresh,  but  as  it  evaporates  it  becomes  highly  charged, 
and  upon  drjdng  leaves  the  salts  in  the  fine  silt  or  on  its  surface.  In 
other  situations  during  dry  seasons  salts  are  frequently  exposed  in 
considerable  quantity,  especially  under  conditions  of  poor  surface- 
drainage.  It  seems  probable,  however,  that  where  the  salts  are  not 
present  in  the  soil  solution  in  sufficient  quantity  to  form  a  visible  crust 
upon  the  surface  of  the  ground  when  the  water  has  evaporated,  as  on 
the  lower  plain  especially,  yet  they  are  relatively  abundant.  This 
characteristic  of  the  soil  of  all  arid  regions  is  probably  nowhere  more 
miarked  than  in  the  vicinity  of  Oodnadatta. 

So  far  as  regards  the  water  relations  of  the  different  physiographical 
areas  mentioned,  it  would  appear  from  inspection  and  from  the 
character  of  the  soil  that  they  may  be  said  to  be  as  various  as  the 
areas  themselves.  At  the  one  extreme  should  be  placed  the  flood-plain 
of  Neales  River,  which  receives  not  only  water  directly  from  the  rains, 
but  also  such  as  comes  to  it  from  the  drainage  of  the  river  system  of 
which  it  is  a  part.  The  gradient  of  the  flood-plain  is  apparently  slight, 
the  soil  is  deep  and  relatively  coarse-grained,  and  there  is  no  continuous 
and  well-defined  channel  at  the  place  visited.  All  of  these  features 
make  for  the  maximum  reception,  storage,  and  retention  of  water.  At 
the  other  extreme  should  probably  be  placed  the  flat-topped  hills, 
representing  the  upper  plain.  Here  the  water  is  merely  lost  and  not 
received  by  run-off,  and  the  soil  is  moistened  directly  by  the  rains  and 
in  no  other  way.  Percolation  of  the  rains  into  the  soil  is  indeed 
forwarded  by  the  presence  of  stones  of  various  sizes,  but  is  relatively 
slow  because  of  the  fineness  of  the  soil.  Only  in  the  slight  depressions 
which  are  the  centers  of  diminutive  drainage  systems  is  there  appre- 
ciable accumulation  of  water  after  rains ;  otherwise,  there  are  no  proper 
soil  reservoirs  for  water  retention.  However,  owing  to  the  closely 
fitted  mosaic,  the  ''gibbers,"  the  water  is  conserved  very  much  better 
than  would  otherwise  be  the  case. 

The  sandhills  and  the  lower  plain  occupy  an  intermediate  position 
with  respect  to  the  water  relation,  although  their  relative  position  is 
not  very  clearly  defined.  So  far  as  regards  the  quality  of  the  soil 
solution  and  the  retention  and  storage  of  the  soil  moisture,  the  sand- 
hills are  to  be  considered  less  arid  than  the  lower  plain,  but  where 
the  latter  joins  higher  ground,  as  the  upper  plain,  it  may  receive 
seepage  water,  and  in  this  regard  only  the  water  relation  of  the  lower 
plain  can  be  said  to  be  more  favorable  than  that  of  the  sandhills.  Other 
than  this  the  water  relations  of  the  lower  plain  are  about  the  same  as 


54  PLANT    HABITS   AND    HABITATS   IN   THE 

the  upper  one.  In  the  vicinity  of  Oodnadatta,  however,  the  soil 
solution  of  the  lower  plain  probably  carries  a  larger  percentage  of  salts, 
which,  as  will  be  remarked  below,  makes  for  physiological  dryness. 
The  sandhills  probably  constitute  excellent  reservoirs  for  water,  and 
through  the  rapid  drying-out  of  the  surface  of  the  soil  the  capillary 
chain  is  broken  and  evaporation  into  the  air  above  the  ground  is  either 
wholly  stopped  or  at  least  it  is  very  decidedly  retarded  and  reduced 
to  a  quantity  that  for  practical  purposes  can  be  neglected.  On  the 
other  hand,  there  are  no  indications  of  water  erosion  among  the  sand- 
hills, and  such  probably  does  not  occur. 

Unlike  soil  of  a  fine  physical  character,  as,  for  example,  that  of  the 
plains,  prompt  penetration  of  the  rains  takes  place  even  if  the  soil 
at  the  time  is  air-dry  and  none  is  lost  by  run-off.  The  dust  mulch 
on  the  surface  is  probably  30  cm.,  more  or  less,  in  thickness,  and  the 
soil  beneath,  of  homogenous  sand,  is  moist  to  a  depth  dependent  only 
on  the  amount  of  the  rains.  The  only  water  lost  from  such  depths  is 
through  the  plant  covering.  The  sandhills,  therefore,  have  water 
relations  which  are  considerably  more  favorable  than  would  appear 
from  a  superficial  examination. 

In  the  other  areas,  such  as  have  poor  surface  drainage,  the  amount 
of  water  received  and  also  in  certain  instances  retained  must  be  said 
to  equal,  if  not  to  exceed,  that  of  any  of  the  other  areas.  In  such 
areas  the  degree  of  aridity  is  related  to  the  concentration  of  the  soil 
solution.  In  the  case  of  the  clay-pans,  for  example,  when  first  flooded, 
as  previously  mentioned,  the  water  is  fresh,  or  but  slightly  brackish, 
and  this  is  indicated  by  the  character  of  the  plant  and  animal  life 
to  be  found  in  them  at  the  time.  As  the  water  escapes  by  evapora- 
tion, however,  the  salts  become  more  and  more  concentrated  until 
only  such  forms  as  are  especially  adjusted  to  withstand  such  dense 
solutions  are  able  to  survive.  Carrying  possibly  not  a  small  amount 
of  moisture,  such  areas  are  nevertheless  intensely  arid,  speaking  in  B. 
physiological  sense. 

From  this  sketch  of  the  leading  physiographic  features  of  the 
vicinity  of  Oodnadatta,  it  can  be  seen  that  there  are  about  four  or  five 
well-defined  plant  habitats.  These  are  the  upper  and  lower  plains, 
the  flood-plain  of  Neales  River  and  its  branches,  the  sandhills,  and 
the  clay-pans,  with  which  might  be  included  other  areas  having  poor 
drainage.  As  will  be  shown  later,  these  areas  have  for  the  most  part 
characteristic  vegetation,  as  might  be  expected  from  their  marked 
dififerences,  some  of  which  have  been  outlined  above. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  55 

CLIMATE. 

Rainfall. 

The  most  arid  part  of  South  Australia,  as  well  as  of  Australia  as  a 
whole,  is  situated  in  the  Lake  Eyre  Basin,  as  has  already  been  pointed 
out.  The  character  of  the  rainfall  for  Oodnadatta  may  be  taken  as 
representative  of  other  portions  of  this  intensely  dry  region.  Ap- 
parently the  station  with  the  least  average  rainfall  is  Kanowana, 
where  it  is  4.33  inches  annually;  at  Oodnadatta,  however,  the  average 
is  4.85  inches.  The  monthly  average  distribution  of  the  rainfall  at 
Oodnadatta  is  given  in  table  12,  which  shows  that  the  seasonal  raina 
are  fairly  equally  divided,  although  averaging  highest  in  the  summer. 
Thus,  at  Oodnadatta  the  average  is  1.80  inches  in  summer,  0.98  inch 
in  autumn,  1.03  inches  in  winter,  and  1.04  inches  in  spring.  As  table 
12  suggests,  the  actual  rainfall  month  by  month  for  different  years  is 
very  unequal  in  amount,  so  that  a  table  of  averages  does  not  have  the 
significance  it  otherwise  might  possess.  The  seasonal  periodicity,  so 
well  marked  over  much  of  the  state,  is  accordingly  not  so  dependable 
at  Oodnadatta  and  in  the  Lake  Eyre  Basin.  However,  as  has  just 
been  indicated,  the  rains  of  summer,  undependable  as  they  may  be 
and  slight  as  they  are,  are  nevertheless  rather  more  in  amount  than 
those  of  any  of  the  other  seasons;  and  it  is  not  impossible  that  the 
adjustment  of  certain  of  the  native  plants  to  their  environment  is 
sufficiently  delicate  so  as  to  largely  hinge  on  just  such  relatively  small 
differences  in  the  seasonal  rainfall.  So  far  as  the  character  of  the 
individual  storms  is  concerned,  relatively  few  of  them  are  of  so  large 
amount  as  to  be  mainly  lost  by  superficial  run-off.  On  the  other 
hand,  a  remarkably  large  percentage  of  the  rainfall  occurs  in  amounts 
too  small  to  directly  benefit  plants.  The  proportion  of  the  total 
rainfall  which  occurs  in  separate  storms,  amounting  to  0.15  inch  or 
less  at  Oodnadatta,  lies  between  about  17  and  56  per  cent  of  that  for 
the  year,  as  shown  by  the  rainfall  records  of  1901-1906,  inclusive 
(table  11).  The  average  monthly  effective  rainfall  for  those  years  is 
as  follows:  January  0.06,  February  0.64,  March  0.03,  April  0.32,  May 
0.24,  June  0.29,  July  0.34,  August,  0.13,  September  0.46,  October 
0.15,  November  0.29,  and  December  0.20  inch.  According  to  these 
records,  therefore,  the  storms  of  summer,  so  far  as  the  effective  rainfall 
is  concerned,  are  considerably  less  than  those  of  winter.  Inasmuch 
as  the  actual  summer  rainfall  exceeds  that  of  winter,  it  would  be  of 
much  interest  and  importance  to  know,  when  a  long  series  of  years  is 
taken  into  account,  whether  over  such  long  period  the  effective  rain- 
fall would  hold  the  relation  above  shown  to  be  the  case  during  the 
years  1901-1906,  inclusive. 


56  PLANT   HABITS   AND   HABITATS   IN  THE 

Temperature. 

As  would  be  expected  from  the  geographical  relations,  including  the 
altitude  of  Oodnadatta  and  of  the  Lake  Eyre  Basin  in  general,  extreme 
temperatures  are  the  rule.  The  summers  are  very  hot,  the  daily 
variation  in  temperature  is  relatively  great,  and  the  minimum  tem- 
peratures of  winter  are  lower  than  might  be  expected  for  the  latitude. 
These  features,  of  course,  are  to  a  large  degree  associated  with  a  low 
rainfall  and  low  relative  humidity.  The  stabilizing  influences  of 
water  and  of  water-vapor  are  largety  wanting.  Thus  the  air,  and 
objects  on  the  surface  of  the  soil,  including  the  vegetation,  are  quickly 
heated  under  the  very  favorable  conditions  of  insolation  obtaining, 
and  conversely  the  radiant  energy  rapidly  escapes  with  the  passing 
of  day.  For  these  reasons  there  are,  as  table  7  indicates,  many  days 
during  the  year  when  the  air  has  a  temperature  of  over  90°  F.,  and, 
on  the  other  hand,  many  nights  when  an  air  temperature  of  less  than 
40°  F.  is  recorded.^  In  fact,  in.  every  month,  except  June  and  July, 
a  temperature  of  90°  F.,  or  above,  is  reached,  and  in  7  months  of  the 
year  the  night  temperatures  drop  to  below  40°  F.  The  extremes  thus 
far  recorded  at  William  Creek,  about  100  miles  from  Oodnadatta, 
are  119°  F.  and  25.3°  F.  for  a  period  covering  28  years. 

A  summation  of  the  mean  monthly  temperature  for  Adelaide,  Port 
Augusta,  Farina,  and  William  Creek  shows  that  the  total  amount  of 
heat  received  increases  at  these  stations  in  the  order  given:  Adelaide, 
747.8°;  Port  Augusta,  793.9°;  Farina,  808°;  William  Creek,  822.6°  F. 

It  is  not  likely  that  the  temperatures  attained  at  Oodnadatta,  or  in 
the  Lake  Eyre  Basin,  are  so  high  as  to  materially  injure  the  perennial 
vegetation.  On  the  other  hand,  a  large  amount  of  heat  is  required  for 
the  growth  and  development  of  such  plants.  Aside  from  this  feature, 
it  is  probable  that  a  leading  effect  of  high  temperatures  on  the  vegeta- 
tion, especially  perennials,  is  an  indirect  one,  namely,  the  effect  of 
such  temperatures  on  the  relative  humidity  of  the  air,  and  hence  on 
the  rate  of  evaporation.  The  capacity  of  the  air  to  absorb  water- vapor 
increases  directly  with  the  temperature.  Hence,  it  is  found  that  the 
drying  power  of  the  air  is  markedly  greater  where  the  temperatures 
are  higher,  other  conditions  being  equal,  than  where  they  are  less. 
The  following  will  illustrate  the  point:  The  average  mean  tempera- 
ture for  Adelaide  is  63°  F.  (17.2°  C);  for  Port  Augusta  it  is  66.2°  F. 
(19°  C.) ;  for  Farina  it  is  67.3°  F.  (19.6°  C.) ;  and  for  William  Creek  it  is 
68.6°  F.  (20.3°  C).  The  weight  of  aqueous  vapor  in  a  cubic  meter  of 
saturated  air  for  these  temperatures  is  as  follows:  14.4,  16.1,  16.6,  and 
17.4  grams,  from  which  it  is  seen  that  an  amount  capable  of  producing 
saturation  under  the  mean-temperature  conditions  at  Adelaide,  and 
assuming  the  equality  of  other  conditions,  would  not  bring  about  satu- 
ration at  William  Creek,  but  only  about  83  per  cent  of  saturation. 

*  See  the  records  for  William  Creek,  table  7. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  57 

GENERAL  FEATURES  OF  FLORA  OF  SOUTH  AUSTRALIA, 
THE  NORTHERN  PORTION  OF  SOUTH  AUSTRALIA. 

The  flora  of  the  northern  portion  of  South  Australia  has  a  marked 
xerophytic  stamp.  As  much,  however,  can  be  said  for  most  of  the 
perennials,  if  not  all,  in  other  portions  of  the  state  having  a  much 
larger  rainfall.  As  Taylor  remarks,  possibly  with  another  idea  in  mind, 
"it  differs  in  degree  according  to  the  rainfall,  but  not  in  kind"  (1918:89). 
This  is  possibly  the  most  remarkable  feature  of  the  vegetation  of  this  in- 
tensely dry  region.  That  is  to  say,  there  are  possibly  no  perennial  forms 
peculiar  to  it  as  such — for  example,  as  the  different  types  of  succulents 
developed  in  other  arid  and  semi-arid  regions,  or  possibly  in  regions 
which  are  desertic.     There  also  are  apparently  no  deciduous  species. 

In  other  dry  regions  some  of  the  species  are  deciduous.  For 
example,  the  acacias  of  the  Sahara,  as  well  as  those  of  the  south- 
western United  States,  have  foliage  which  falls  away  with  the  seasons; 
and  in  the  arid  southwestern  part  of  the  latter  country  a  species 
(Fouquieria  splendens)  occurs  which  is  deciduous  with  respect  to  the 
occurrence  of  the  rains,  losing  and  forming  the  foliage  perhaps  several 
times  during  the  year,  in  a  manner  directly  connected  with  the  rains 
and  the  intervening  dry  spells.  Therefore,  there  may  be  possible 
not  -a  little  variation  in  plants  in  extremely  arid  regions.  Thus, 
although  the  perennial  flora  of  the  far  north  has  apparently  Httle  or 
no  striking  peculiarities  which  set  it  apart  from  that  of  the  regions  of 
South  Australia  more  highly  favored  with  rainfall,  there  is  still  not  a 
little  diversity  in  it. 

Among  the  most  interesting  trees  of  the  dry  region  are  several 
species  of  Acacia  which  show  important  morphological,  as  well  as 
physiological,  differences.  Certain  of  the  hakeas  exhibit  remarkable 
differences  as  between  species  and  marked  adjustment  to  an  arid 
envu-onment.  Of  the  shrubs,  those  of  the  genus  Eremophila  are  of 
especial  interest.  Out  of  the  39  species,  including  those  now  put 
under  PhoUdia,  Tate  gives  17  species  as  occurring  in  the  northern 
portion  of  the  state.  Of  the  shrubs,  this  is  the  desert  plant  par 
excellence.  But  the  halophytes  of  whatever  species  constitute  the 
most  prominent  element  of  the  flora  of  this  region.  Tate  gives  54 
species  of  the  Chenopodiacese  and  Amarantacese  from  the  far  north, 
most  of  which  are  highly  salt-resistant.  There  are  a  few  succulent 
annuals,  or  half  shrubs.  Among  these  are  species  of  the  Zygophyl- 
lacese  and  Calandrinia  halonnensis  (Portulacese) ;  the  latter  bears  large, 
succulent  leaves  and  is  much  sought  after  by  animals.  Stuart's  pea, 
Clianthus  dampieri,  is  one  of  the  most  showy  of  the  annuals. 

Of  the  grasses,  among  the  most  frequently  met  are  the  "bunch" 
forms,  as  Triodia  irritans  and  Spinifex  paradoxus,  which  are  widely 
distributed  in  the  interior  of  the  continent.     In  addition,  according  to 


58  PLANT   HABITS   AND    HABITATS   IN   THE 

Tate,  there  are  55  species  of  grasses,  mainly  annual,  which  are  to  be 
found  also  in  northern  South  Australia.  These  for  the  most  part  are 
to  be  seen  only  after  rains,  possibly  mainly  those  of  summer. 

'   VEGETATION  OF  THE  LAKE  EYRE  BASIN. 

As  one  enters  the  Lake  Eyre  region  by  the  railway,  the  general  im- 
pression is  had,  which  becomes  stronger  upon  further  acquaintance 
with  the  region,  that  the  total  amount  of  perennial  vegetation  has 
suddenly  become  less,  despite  the  large  halophytic  population.  More- 
over, the  larger  elements  of  the  vegetation  are  more  and  more  re- 
stricted to  the  water-courses  and  a  relatively  small  amount  is  to  be 
seen  venturing  away  from  them.  The  differences  noted  are  possibly 
most  marked  with  the  tree  flora.  Clearly  such  a  generalized  statement 
is  difficult,  if  not  impossible,  to  demonstrate.  One  would,  of  course, 
expect  a  falling  off  in  the  amount  of  vegetation  in  a  region  having  only 
5  inches  as  opposed  to  one  having  nearly  9  inches — for  example, 
that  about  Copley.  But  the  point  I  wish  to  make  is  that  the  differ- 
ence is  greater  than  the  difference  in  the  recorded  rainfall  would  lead 
one  to  expect.  To  illustrate  the  idea  crudely,  we  may  suppose  the 
amount  of  vegetation  and  the  amount  of  rainfall  to  be  represented  in  a 
figure  by  two  curves.  The  curve  representing  the  amount  of  vegeta- 
tion is  assumed  to  decline  parallel  to  that  representing  a  decrease  in  the 
precipitation.  However,  with  the  decreased  rainfall  there  comes  a 
rapid  increase  of  other  chmatic  factors  making  for  aridity,  and  espe- 
cially there  occurs,  in  the  Lake  Eyre  region,  a  relatively  large  proportion 
of  non-effective  precipitation.  We  therefore  get  a  diverging  of  the 
vegetation-rainfall  curves  which  at  the  last  is  very  sharp.  The  sudden 
falling  of  the  vegetation  curve  I  believe  to  be  directly  related  to  the 
large  percentage  of  non-effective  rainfall,  although  with  it  there 
naturally  must  be  associated  an  intensification  of  other  environmental 
physical  factors  working  toward  the  same  end.  In  other  words,  the 
effect  is  as  if  in  place  of  contrasting  regions  having  about  5  and  9  inches 
of  rain,  we  are  contrasting  regions  whose  effective  rainfall  may  be  said 
to  be  about  3  and  possibly  8  inches. 

VEGETATION  AT  OODNADATTA. 

A  general  idea  of  the  amount  of  the  perennial  vegetation  in  the  vicin- 
ity of  Oodnadatta  may  be  had  by  ascending  O'Halloran's  Mount, 
which  is  about  4  miles  to  the  north  of  the  village  (plate  1a).  This 
low  hill  is  evidently  a  detached  portion  of  the  upper  plain  and  it  com- 
mands a  very  good  view  of  the  desert.  As  one  surveys  the  surrounding 
country  he  is  at  first  struck  with  the  paucity  or  rather  with  the  want  of 
plant  covering.  In  every  direction  the  wide-spreading  plains  and 
flat-topped  hills  appear  quite  barren.  The  gibbers  glisten  hke  polished 
mirrors  in  the  sun,  but  otherwise  a  monotonous  reddish-brown  color 
prevails.    There  are  thus  apparently  no  plants  to  enliven  the  scene. 


ARID   PORTIONS   OP   SOUTH   AUSTRALIA.  59 

The  effect  is  as  if  no  living  thing  ever  found  or  ever  could  find  a  lodg- 
ment and  an  abiding-place  in  the  expanding  waste.  More  careful 
examination,  however,  reveals  the  presence  of  plants.  Across  the 
lower  plain,  for  example,  there  extend  narrow  ribbons  of  vegetation. 
These  converging  make  gray-green  bands  and  mark  the  drainage 
channels  where  only  masses  of  vegetation  are  to  be  found.  The  in- 
consequential plant  Hfe  of  the  plains  as  a  whole  does  not  appear  on  such 
a  general  view.  Slight  as  is  the  present-day  vegetation  of  the  region, 
it  perhaps  is  a  matter  for  surprise  that  there  is  so  much.  Aside  from 
the  unfavorable  physical  environmental  conditions  which  make  for 
few  plants,  there  are  also  biotic  environmental  elements  which  are 
relatively  very  destructive.  Thus  the  region  has  supported  and  now 
supports  an  aboriginal  population  which  depends  wholly  on  natural 
products,  animal  and  vegetable,  for  its  living;  and  relatively  recently 
the  white  inhabitants  have  drawn  heavily  on  every  useful  native  plant. 
Herbivorous  animals  of  many  kinds  have  also  made  destructive 
inroads  on  the  vegetation.  Just  how  all  of  these  biotic  factors  have 
affected  the  flora  as  a  whole  will,  of  course,  never  be  known,  but  that 
they  are,  and  long  have  been,  of  great  importance  in  many  ways  can 
not  be  seriously  questioned. 

VEGETATION  OF  THE  PLAINS. 

The  vegetation  of  the  plains  was  observed  in  four  separate  localities 
on  the  upper  and  on  the  lower  plains.  So  far  as  these  situations  are 
concerned  the  perennial  vegetation  was  found  to  be  very  meager  indeed, 
but  there  were  a  few  annuals  which  had  sprung  up  following  a  small 
rain  of  the  week  preceding  my  visit.  Both  classes  of  vegetation,  how- 
ever, were  for  the  most  part  restricted  in  distribution  to  the  small  and 
sUght  depressions  on  the  plains  or  to  the  diminutive  drainage  channels 
frequently  associated  with  them.  Taken  as  a  whole,  aside  from  such 
relatively  favorable  situations  as  above  mentioned,  the  plains  gave 
little  suggestion  of  plant  life.  Among  the  annuals  were  found  Bra- 
chycome  ciliaris  and  Senecio  gregorii,  and  among  the  perennials  Bassia 
lanicuspisi'l) ,  which  occurred  very  sparingly,  and  species  of  Eremo- 
phila.  The  Eremophilas  were  the  most  striking  and  interesting  of  the 
perennials.  Of  these,  Eremophila  freelingii  (plate  2,  a  and  b;  plate  3b) 
appeared  to  be  most  numerous  and  was  found  on  both  plains.  Plate 
2b  shows  a  typical  example  of  the  species  in  place  on  the  upper  plain. 
It  is  a  much-branched  shrub  about  a  meter  in  height  and  bears  dull- 
green  leaves,  narrowly  oblong  in  form,  mostly  at  the  end  of  the 
branches.  The  species  is  fairly  rare  on  the  plains,  but  in  and  along 
the  drainage  channels  the  population  is  more  abundant  and  the  indi- 
viduals of  a  larger  size  than  on  the  plains  proper.  In  addition  to  the 
species  referred  to,  E.  latrohei  (plate  3c)  has  a  distribution  about  like 
that  of  E.  freelingii,  but  is  possibly  not  so  abundant.    In  a  wash  at  the 


60  PLANT   HABITS   AND   HABITATS   IN   THE 

south  base  of  O'Halloran's  Mount  may  be  found  E.  negleda  (plate  5b). 
In  the  same  situation  a  few  examples  of  an  undetermined  half -shrub  and 
several  annuals,  also  undetermined,  were  seen. 

Although  the  species  mentioned  in  the  preceding  paragraph  are 
to  be  found  very  sparingly  on  both  the  upper  and  the  lower  plains, 
the  former  was  especially  in  mind  when  writing  the  description; 
and,  so  far  as  one  can  judge,  the  vegetation  of  this  plain,  at  least  in  the 
vicinity  of  Oodnadatta,  has  been  little  affected  by  the  presence  of  man. 
No  trees  occur  on  it  and  the  shrubs  of  the  plain  are  apparently  not 
found  useful  either  by  man  or  beast.  On  the  lower  plain,  however, 
there  are  indications  that  formerly  the  number  of  individuals  may 
have  been  greater  than  now.  Dried  remains  of  salt  bushes  are  to  be 
found  here  and  there,  and  persons  familiar  with  the  region  say  that 
such  forms  were  formerly  fairly  abundant  on  this  plain.  It  seems  prob- 
able, also,  that  after  heavy  rains,  which  occur  at  widely  separated 
intervals,  the  face  of  the  lower  plain  may  be  clothed  with  annuals, 
including  grasses,  and  that  they  may  be  of  such  size  and  abundance 
as  to  completely  hide  the  surface  of  the  ground;  and,  although  there 
are  no  trees  on  this  plain,  they  may  be  found  along  water-courses  con- 
necting it  with  the  upper  plain — for  example,  Acacia  camhadgei  occurs 
sparingly  in  such  a  drainage  channel  leading  from  the  upper  to  the 
lower  plain  at  a  place  about  4  miles  to  the  west  of  Oodnadatta  (plate  3a). 
Eremophila  neglecta  and  E.  latrohei  also  occur  in  such  situations. 

VEGETATION  OF  AND  ABOUT  THE  SANDHILLS. 

Across  the  lower  plain  and  about  3  miles  to  the  east  or  southeast  of 
Oodnadatta  is  an  area  where  sandhills  and  clay-pans  are  the  most 
characteristic  features  of  the  physiography.  On  the  way  to  the  hills 
the  plain  is  found  to  sustain  a  sparse  population  of  saltbushes  of  various 
kinds  which  were  not  studied  particularly,  and  viewed  from  the  plain 
the  distant  sand  ridges  appear  to  be  fairly  well  covered  with  vegetation. 
Upon  drawing  near  the  hills  a  comparatively  large  number  of  small 
trees  and  shrubs  are  also  to  be  seen.  But  the  near  view  of  the  sandhills 
reveals  the  fact  that  the  vegetation  is  very  diffuse  and  composed 
almost  exclusively  of  a  single  form.  The  clay-pans  which  lie  between 
or  by  the  sandhills  were  found  to  be  devoid  of  vegetation,  although 
when  flooded  such  a  form  as  the  "nardoos,"  Marsilia  spp.,  nmy  be  found. 
On  the  rims  of  the  clay-pans  saltbushes  occur,  but  not  in  abundance. 

The  characteristic  species  of  the  sandhills  is  the  sandhill  mulga. 
Acacia  linophylla.  On  the  dunes  the  species  has  the  habit  of  a  large 
shrub,  but  occasionally  a  central  stem  is  formed.  It  is  about  5  meters 
in  height.  The  habit  of  the  species  is  shown  in  plate  4b.  The  leaves, 
or  rather  phyllodia,  are  relatively  few  in  number  (plate  5a),  about 
15  cm.  in  length  and  about  2  mm.  wide.  They  are  fairly  rigid  and 
have  an  attenuated  but  not  a  spiny  tip.    At  the  time  of  my  visit, 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  61 

July  11,  the  species  was  flowering  and  the  plants  were  covered  with 
ants  in  immense  numbers,  which  appeared  to  be  seeking  the  nectar  of 
the  flowers.  The  small  size  of  the  trees  and  the  large  amount  of  dead 
wood  attested  to  the  very  difficult  conditions  under  which  the  species 
was  living.  So  far  as  the  roots  could  be  seen,  it  was  found  that  many 
were  very  near  the  surface,  being  often  exposed  through  wind  erosion. 
Although  no  long  horizontal  roots  were  found,  it  is  known  that  in  the 
mulga  and  under  analogous  conditions  very  long  superficial  roots  are 
formed.  Owing  to  this  fact  and  to  their  being  of  a  fairly  uniform 
size,  they  are  used  by  the  aborigines  in  the  making  of  spear  handles. 
Although  the  mulga  was  the  only  woody  perennial  found  in  the  sand- 
hills, a  species  of  "spinifex"  or  bunch  grass  appears  here  and  there,  and 
is  one  of  the  most  characteristic  plants  of  the  arid  interior. 

On  the  plain  and  at  a  relatively  short  distance  from  the  base  of  the 
sandhills  some  shrubs  and  trees  are  to  be  found.  In  places  they  are 
relatively  abundant  and  also  fairly  large.  The  shrubs  are  wholly  or 
mainly  Eremoyhila  neglecta  (plate  5b),  about  2  meters  high  and  well 
clothed  with  leaves.  The  trees  are  of  but  a  single  species,  ''dead 
finish,"  Acacia  tetragonophylla,  which  is  of  wide  occurrence  in  the 
drier  portions  of  South  Australia.  The  habit  of  the  species  is  shown 
in  plate  4a  and  plate  6a.  A  leading  and  striking  characteristic  of  the 
latter  species  lies  in  the  small  size  of  the  phyllodia,  which  are  borne  in 
relatively  large  numbers,  faMy  well  distributed  on  the  smaller  branches. 
The  relative  abundance  of  the  species  at  the  base  of  the  sandhills  is 
apparently  attributable  directly  to  the  comparatively  favorable  water 
relations  of  the  place. 

The  soil  is  fairly  deep  and  covered  with  a  sand  mulch  blown  from  the 
neighboring  hills.  There  is  a  substratum  of  a  white  and  not  especially 
hard  material  which  has  the  appearance  of  travertine  limestone  and 
indeed  may  be  that.  Whether  this  prevents  the  deeper  sinking  of 
water  or  absorbs  it,  to  be  yielded  again  to  the  plant-roots,  was  not  de- 
termined. In  case  the  substratum  underlies  the  sandhills  as  well, 
which  may  be  the  case,  a  further  reason  for  the  relatively  abundant 
vegetation  at  their  base  would  be  found.  So  far  as  the  substratum  is 
concerned,  it  was  found  to  crop  out  along  the  path  to  the  hills,  and  in 
such  cases  it  formed  a  hard  surface  quite  as  in  the  "caliche,"  or  desert 
limestone,  in  the  more  arid  parts  of  the  United  States,  in  southern 
Algeria,  and  other  dry  regions.  Moreover,  under  such  conditions  it  is 
fairly  impervious  to  water. 

In  the  habitat  at  the  base  of  the  sandhills  there  were  found  a  few 
specimens  of  the  phanerogamous  parasite  Loranthus  exocarpi  on 
Eremophila  neglecta.  The  paucity  of  this  type  of  vegetation  in  the 
vicinity  of  Oodnadatta  forms  a  striking  contrast  to  the  conditions 
obtaining  at  Copley,  where  the  mistletoes  are  very  numerous. 


62  PLANT   HABITS   AND   HABITATS   IN   THE 

Although  there  is  thus  seen  to  be  a  comparatively  abundant  peren- 
nial flora  at  and  near  the  sandhills,  yet  the  largest  number  of  woody 
plants  about  Oodnadatta,  especially  the  largest  number  of  trees,  is 
to  be  found  in  water  channels  of  whatever  kind,  either  Neales  River 
or  washes  at  the  bases  of  the  fiat-topped  hills.  As  viewed  from  the 
vantage-point  of  the  upper  or  even  the  lower  plain  (plate  5c),  the 
Neales  River  bottoms  has  a  considerable  tree  population,  and  par- 
ticularly a  large  number  of  shrubs.  The  present-day  shrub  and  tree 
population  of  the  flood-plain  of  the  river  can  not  be  taken  as  indicative 
of  what  must  have  been  the  condition  in  earlier  times.  The  inhabitants 
of  the  nearby  town  have  actively  removed  all  trees  large  enough  to 
supply  fuel.  The  shrubs,  however,  have  probably  very  largely  escaped 
such  inroads.  The  same  remark  would  also  apply  to  the  neighboring 
washes,  where  the  water  relations  are  suitable  for  some  tree-growth. 

Of  the  species  now  to  be  found  on  the  flood-plain  of  Neales  River, 
the  most  conspicuous  are  Eucalyptus  rostrata  (plate  4c)  and  species 
of  Acacia,  among  which  are  A.  camhadgei,  A.  tetragonophylla,  and  A. 
stenophylla.  There  are  also  several  species  of  saltbushes,  several 
shrubs  whose  identity  was  not  determined,  and  some  annuals.  Of  the 
trees.  Acacia  camhadgei  is  possibly  the  most  numerous.  This  is  the 
"stinking"  acacia,  or  ''gidya,"  the  name  given  it  by  the  aborigines, 
which  is  said  to  refer  to  an  edible  (for  aborigines!)  larva  which  is  to  be 
found  beneath  the  bark.  The  tree  attains  a  height  of  10  meters  or 
more  and  has  a  compact  habit  of  growth.  Like  the  other  species  of 
Acacia  growing  in  the  far  north,  true  leaves  are  not  present  on  the 
mature  plant,  but  their  place  is  taken  by  phyllodia.  In  the  case  of  the 
gidya  the  phyllodia  are  fairly  large  as  well  as  abundant,  so  that  a 
distinctly  leafy  effect  is  produced  (plate  6a)  and  the  shade  cast  is 
dense — a.  rare  occurrence  in  desert  plants. 

A.  tetragonophylla  is  also  a  small  tree,  but  with  a  foliar  habit  quite 
different  from  the  species  last  mentioned.  Its  phyllodia  are  needle- 
form,  8  to  28  mm.  in  length,  and  may  occur  in  groups  of  a  few  each. 
They  fall  away  fairly  easily  and  the  ground  beneath  the  trees  is  usually 
thickly  covered  with  them.  It  appears  probable  that  the  shedding 
of  the  phyllodia  should  be  considered  a  very  effective  means  of  re- 
ducing the  evaporation  surface  and  hence  of  cutting  down  excessive  loss 
of  water  during  especially  severe  drought.  The  foliar  habit  of  A. 
stenophylla  is  unhke  that  of  either  of  the  species  above  mentioned. 
The  species  is  a  small  tree  or  a  large  shrub  at  Oodnadatta  and  true 
leaves  are  formed  on  young  shoots,  although  they  are  soon  cast  off, 
phyllodia  taking  their  place  (plate  6b).  The  phyllodia  are  various 
as  to  form  and  size,  but  in  general  they  are  long,  narrow,  and  even 
linear  in  the  extreme  form.  In  the  portions  of  a  plant  which  are  sub- 
jected to  the  most  intense  illumination  the  phyllodia  assume  an  up- 
right position,  but  where  shaded  they  are  pendant. 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  63 

The  root-habits  of  certain  species  growing  along  the  washes  or  by 
the  separate  basins  on  the  flood-plain  of  Neales  River  were  studied 
as  far  as  possible.  Observations  of  roots  exposed  by  the  washing  away 
of  the  banks  indicate  that  the  general  course  of  the  roots  of  the  trees 
was  similar.  Taking  Eucalyptus  rostrata  and  Acacia  cambadgei, 
especially,  it  was  found  that  a  prominent  portion  of  the  root-system  is 
made  up  of  large  horizontal  members  which  may  extend  for  a  long  dis- 
tance from  the  central  stem  (plate  7a).  Thus  the  superficial  roots  of 
Eucalyptus  were  seen  to  reach  out  9  meters  or  more  and  to  lie  at  a 
depth  not  exceeding  60  cm.,  although  the  distance  beneath  the  surface 
of  the  ground  was  usually  much  less.  In  addition  to  horizontal  roots, 
vertical  ones  were  found,  but  none  lying  at  angles  between.  In  the 
case  of  several  shrubs  whose  roots  were  observed,  it  was  found  that  an 
analogous  condition  obtained — that  is,  there  was  evidence  of  direct 
reaction  to  the  type  of  rainfall  which  is  especially  characteristic  of  the 
region.  In  Acacia  stenophylla  shoots  arise  from  the  superficial  roots 
(plate  7b),  with  a  resulting  and  characteristic  dense  thicket  formation. 
Such  vegetative  reproduction  was  seen  in  several  species  in  the  other 
regions  visited,  especially  at  Quorn. 


64  PLANT   HABITS   AND   HABITATS   IN  THE 

THE  COPLEY  ENVIRONMENT. 
PHYSIOGRAPHY. 

The  topography  and  hence  the  plant  habitats  in  the  immediate  neigh- 
borhood of  Copley  are  extremely  varied,  owing  mainly  to  the  relation 
of  the  region  to  the  Flinders  Mountains.  The  main  portion  of  the 
north  end  of  the  Flinders  hes  to  the  east,  between  Copley  and  Lake 
Fromme,  but  a  lesser  part  is  between  the  village  and  Lake  Torrens 
on  the  west.  Copley  is  thus  in  the  bifurcation  of  the  range,  with  out- 
lying hills  and  low  mountains  within  one  mile  or  more  on  either  side. 
The  plain  at  Copley  constitutes  little  more  than  a  valley,  but  it  widens 
to  the  north,  becomes  lower  in  altitude,  and  soon  constitutes  a  leading 
feature  of  the  topography.  Copley  lies  between  the  500-foot  and 
1,000-foot  contours  and  hence  is  near  the  upper  level  of  the  Cretaceous 
beds  (Taylor,  1918:87).  In  the  Flinders  to  the  east  are  peaks  which 
are  among  the  highest  of  the  entire  ranges,  including  Mount  Serle, 
the  Freehng  Heights  (3,120  feet),  and  Mount  Benbonyanthe  (3,470 
feet).  The  altitude  of  the  division  of  the  Flinders  to  the  west  of 
Copley  is  2,000  feet  or  less.  The  observations  upon  which  the  present 
study  is  based  were  made  within  a  15-mile  radius  of  Copley  and  were 
confined  to  an  altitudinal  range  of  approximately  1,000  feet.  Within 
this  small  region,  however,  there  is  to  be  found  a  bewildering  array  of 
hills,  valleys,  slopes,  washes,  and  flats  which  would  be  beyond  the  pur- 
poses of  this  study  to  describe  accurately  or  in  detail.  The  device 
will  be  resorted  to,  however,  of  attempting  a  characterization,  so 
far  as  possible  from  the  data  at  hand,  of  such  of  the  habitats  as  appear 
to  be  of  most  interest  in  connection  with  this  study. 

The  Flinders  on  either  side  of  Copley  are  for  the  most  part  of  the 
Cambrian  age,  but  there  are  also  Mesozoic  rocks.  Thus  the  slate  hills 
with  vertical  strata  to  the  east  of  the  town  are  possibly  of  the  former, 
and  the  table  mountain  just  southeast  is  of  Mesozoic.  The  latter  is 
part  of  the  desert  sandstone  previously  seen  at  Oodnadatta  and  which 
formerly  extended  over  most  of  central  and  northern  Austraha  (How- 
chin  and  Gregory,  1909:93).  Thus  the  underlying  rocks,  and  conse- 
quently the  soil  derived  by  disintegration  from  them,  have  a  widely 
different  physical  character.  Future  ecological  studies  in  the  vicinity 
of  Copley  may  well  correlate  the  distribution  of  the  vegetation  with 
the  nature  of  the  soil  and  with  the  rocks  from  which  it  has  been  derived, 
as  has  been  done  by  Osborne  in  the  Mount  Lofty  Ranges  near  Adelaide 
(1914:114). 

Such  observations  as  were  made  by  me  on  soils  will  be  given,  to- 
gether with  the  running  account  of  the  most  striking  features  of  each 
of  the  habitats  studied.  It  will  suffice  to  say,  as  would  be  supposed 
from  what  is  known  of  the  local  geology  as  above  suggested,  that  the 
soils  are  very  various.     For  example,  on  the  plain  about  the  village 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  65 

there  is  a  large  amount  of  sand,  some  of  fine  grain  and  easily  shifting 
with  the  wind.  For  this  reason  one  finds  fences  covered  with  sand 
drift  and  sandy  hillocks.  There  are  also  a  few  moving  dunes  of  small 
size.  In  the  low  hills  the  soil  appears  to  be  all  or  part  clay,  or  at  least 
of  very  fine  structure,  as  a  sandy  loam.  There  is  evidently  very  little 
humus.  So  far  as  the  depth  of  the  soil  is  concerned  it  can  be  said  to 
vary  greatly.  On  the  plain  near  Copley  it  is  4  meters  or  more.  Among 
the  hills,  on  the  other  hand,  there  are  many  areas  where  the  rock  is 
barely  covered  with  soil,  and  of  course  there  are  many  outcrops  in 
which  soil  is  entirely  wanting.  In  any  region,  such,  for  example,  as 
that  about  Copley,  where  a  small  rainfall  is  a  prominent  environmental 
factor  of  plants,  the  nature  of  the  soil,  including  its  depth,  is  of  very 
great  importance  in  shaping  the  character  of  the  plant  covering  as 
well  as  its  distribution.  This  fact  is  largely  based  on  the  circumstance 
that  the  soil  constitutes  the  sole  reservoir  for  the  reception  and  storage 
of  water. 

Owing  to  the  broken  topography  the  water-courses  of  the  region  are 
not  only  numerous  but  also  in  many  regards  extremely  varied.  In 
some  the  gradient  is  marked,  in  others  it  is  relatively  slight.  The 
channels  may  be  very  well  developed  and  hence  considerably  below 
the  adjoining  plain,  or  slope,  as  the  case  may  be,  or  the  converse  may 
be  true.  The  leading  drainage  channels  of  all  sorts  are  contributory  to 
Leigh's  Creek.  This  stream,  dry  much  of  the  year,  takes  its  origin  a 
few  miles  to  the  east  of  Copley  in  the  Flinders  Ranges,  and  running 
northward  it  joins  the  Fromme  River  and  ultimately  discharges  into 
Lake  Eyre.  To  the  south  of  Copley,  and  a  Uttle  beyond  the  region 
studied,  the  streams  run  in  the  opposite  direction  and  into  or  toward 
Lake  Torrens.  Although  the  drainage  is  generally  very  well  defined, 
there  are  relatively  small  separated  basins,  mainly  on  the  Copley 
plain,  which  have  inadequate  drainage  or  no  surface  outlet.  In  such 
depressions  there  is  a  large  accumulation  of  salts. 

It  will  be  seen  from  the  above  sketch  that  the  leading  physiographic 
divisions  or  units  can  be  said  to  be  the  hills,  the  Copley  Plain,  and  the 
washes.  For  convenience,  the  hills  will  be  divided  into  (1)  the  Mount 
Deception  Range,  such  of  the  Flinders  Ranges  as  lie  to  the  west  of 
Copley,  and  (2)  Table  Mountain  and  Mount  of  Light,  with  the  nearby 
hills,  to  the  east.  For  the  purpose  of  further  distinguishing  the  locali- 
ties to  be  referred  to  below,  they  will  be  mentioned  in  reference  to  the 
roads  which  lead  to  them,  as  follows : 

North  of  town:  Myrtle  Springs  road  crosses  the  plain  northwest  of  the 
village,  goes  through  the  low  hills  to  the  east  of  the  Mount  Deception 
Range,  and  finally  through  that  range.  Yudnamutana  road  goes  north 
and  northeast  of  town,  passes  along  the  western  side  of  the  Flinders 
Ranges,  and  at  length  penetrates  them;  this  road  also  crosses  the  plain 
and  runs  over  low  hills,  where  it  passes  out  of  the  Copley  vicinity. 


66 


PLANT   HABITS   AND    HABITATS   IN   THE 


East  of  town:  The  Mount  Serle  road  crosses  the  plain  for  about  a 
mile  and  then  enters  the  undulating  hill  country.  It  passes  to  the 
north  of  the  Mount  of  Light,  and  winds  between  lower  hills  until  it 
also  passes  beyond  the  Copley  district. 

South  of  town:  The  Beltana  road  goes  in  the  midst  of  the  Copley 
Plain  for  several  miles  and  at  length  makes  its  tortuous  way  through 
the  Flinders  to  Beltana  and  southern  towns. 

CLIMATE. 
Rainfall. 

The  climate  of  Copley  can  be  characterized  as  arid,  with  cool  winters 
and  hot  summers.  Owing  to  its  position,  about  midway  between  the 
southern  extension  of  the  summer  rains  and  the  northern  limit  of 
those  of  winter,  some  precipitation  is  to  be  expected  in  every  month  of 
the  year;  for  the  same  reason,  the  rainfall  of  any  season  is  extremely 
variable.  In  table  13  are  presented  rainfall  data  for  a  period  of  35 
years,  supplied  by  the  Commonwealth  Bureau  of  Meteorology.     It  will 

Table  13. — Average  rainfall  at  Copley  {Leigh's  Creek),  South  Australia,  based  on 
records  for  36  years. 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

Mean 

Highest 

0.67 
4.76 

0.62 
3.05 

0.80 
4.70 

0.54 

3.78 

1.06 

5.84 

1.11 
4.72 

0.60 
2.24 

0.69 
3.02 

0.75 
3.58 

0.47 
2.06 

0.53 
2.35 

0.76 

3.78 

8.40 
16.64 
1.54 

be  seen  that  the  extreme  variation  in  yearly  precipitation  is  from  L54 
to  15.64  inches.  The  seasonal  averages  are  as  follows:  Summer,  1.95; 
autumn,  2.4;  winter,  2.3;  and  spring,  1.76  inches.  Another  feature 
of  the  rainfall  at  Copley  does  not  appear  in  the  table,  but  was  seen  in 
daily  reports  very  kindly  put  at  my  disposal  by  Mr.  Bromley,  meteor- 
ologist at  Adelaide.  This  relates  to  the  maximum  rainfall  for  one  day. 
Records  covering  6  years,  1901  to  1906,  inclusive,  were  examined.  The 
greatest  rain  for  24  hours  during  this  period  was  on  December  28, 1903, 
when  3  inches  were  reported.  This,  it  will  be  noted,  is  about  twice 
as  much  as  occurred  during  the  year  of  minimal  rain  as  given  in  the 
table. 

The  rainfall  at  Copley,  however,  as  has  been  shown  in  another  place, 
is  not  always  in  amount  sufficient  to  be  of  direct  use  to  plants.  In  fact, 
it  was  shown  that  for  the  years  1901  to  1906,  inclusive,  approximately 
19  per  cent  of  the  rain  occurred  in  showers  of  0.15  inch  or  less.  The 
amount  of  0.15  inch  rainfall  was  placed  as  the  minimum  after  the 
following  observations  had  been  made  at  Copley,  supplemented  by 
others  at  Ooldea.  On  August  20,  after  a  slow  rain  amounting  to 
0.21  inch,  fairly  fine  soil  containing  some  sand  on  the  plain  was  found 
to  have  been  moistened  to  a  depth  of  4  cm.,  and  coarser  soil  also  on 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA;  67 

the  plain  was  wetted  to  a  depth  of  8  to  9  cm.  The  observations  were 
repeated  a  few  days  later  with  substantially  the  same  results.  In  both 
instances  the  rains  were  followed  by  drying  weather,  so  that  a  large 
percentage  of  the  moisture  taken  into  the  soil  must  have  been  lost 
quickly  by  evaporation.  It  was  assumed  that  had  the  rainfall  been 
25  per  cent  less,  the  penetration  would  also  have  been  very  much  less, 
and  the  amount  of  water  lost  by  evaporation  would  bave  been  rela- 
tively greater  with  respect  to  the  amount  recorded.  Therefore, 
under  such  conditions  there  would  be  very  little,  if  any,  available  for 
the  use  of  plants,  more  especially  for  the  use  of  perennials.  However, 
as  will  be  shown  below,  there  is  no  doubt  that,  given  favorable  soil 
conditions,  a  rain  amounting  to  0.20  inch  penetrates  the  soil  suffi- 
ciently to  moisten  the  horizon  occupied  by  the  roots  of  many  annuals 
and  also  by  a  portion  of  the  horizontal  roots  of  certain  perennials. 

Temperature. 

The  temperature  records  for  Copley  were  not  examined  by  me,  but 
the  Commonwealth  Bureau  of  Meteorology  very  kindly  supplied  the 
records  for  Farina,  40  miles  farther  north,  which  have  been  accepted 
as  illustrating  the  conditions  at  Copley.  A  summary  of  these  records 
for  Farina  has  been  given  in  table  7,  which  shows  that  the  highest 
shade  temperature  reported  for  the  station,  for  a  period  of  28  years, 
was  119°  F.  The  absolute  minimum  was  25.3°  F.  The  annual  range 
may  be  considerable;  for  example,  in  1912  the  minimum  reported 
was  27.3°  F.  and  the  maximum  was  118°  F.,  a  total  range  of  90.7°  F. 
During  the  same  year  the  mean  daily  range  was  18.6°  F.  and  the  maxi- 
mum range  observed  during  the  course  of  one  day  was  53°  F.  The 
mean  yearly  temperature  at  Farina  is  more  than  10°  F.  below  that  at 
William  Creek,  as  representing  Oodnadatta,  and  it  is  nearly  4°  higher 
than  that  at  Adelaide.  For  other  details,  reference  can  be  had  to 
table  7. 

VEGETATION  OF  THE  COPLEY  REGION. 

The  most  striking  features  of  the  flora  of  the  lowlands  between 
Marree  (Hergott  Springs)  and  Copley  are  its  abundance  and  the  fact 
that  it  is  practically  all  of  one  type,  namely,  halophytes.  Viewed  from 
some  distance,  the  relatively  slight  individuality  of  the  species  is  lost 
and  the  plains  appear  closely  covered  with  a  uniform  growth.  In  and 
along  washes  and  on  the  slopes  of  the  hills,  however,  the  vegetation  is 
generally  composed  of  sclerophyllous  shrubs  and  trees  which  vary 
greatly  in  size,  form,  and  occurrence.  Even  at  this  day,  and  in  spite 
of  the  heavy  demands  of  whatever  nature  made  on  the  native  vegeta- 
tion by  the  white  inhabitants,  there  is  a  remarkable  wealth  of  plants, 
not  only  as  regards  species  but  also  as  to  number  of  individuals;  and 
it  is  to  be  remembered  that  the  rainfall  of  the  region  is  by  no  means 
heavy.    At  Marree  it  is  6.08  inches  and  at  Copley  8.40  inches,  of 


68  PLANT   HABITS   AND   HABITATS   IN   THE 

which  about  20  per  cent  occurs  in  amounts  too  small  to  benefit  plants 
directly. 

The  following  glimpses  of  the  vegetation,  its  leading  character,  and 
occurrence,  taken  at  a  few  well-marked  localities  close  to  Copley, 
should  supply  in  a  broad  way  sufficient  data  to  reconstruct  its  general 
features. 

For  convenience  the  description  of  the  vegetation  at  Copley  will  be 
grouped  around  the  following  physiographic  units  (habitats),  which 
will  be  made  the  centers  of  ''communities,"  but  they  are  probably  not 
of  equal  value,  as  will  be  at  once  apparent : 

(1)  "Alkali"  plains,  or  lowlands,  including  slopes  and  benches  where 
halophytic  vegetation  points  to  an  excess  of  salts  in  the  soil. 

(2)  Low  hills  and  the  slopes  of  higher  hills,  or  low  mountains,  as 
of  the  Mount  Deception  Ranges  west  of  Copley  and  the  lower  portions 
of  the  Flinders  Ranges  to  the  east.  This  includes  the  subaerial  delta 
fans(?)  on  either  side  of  the  Copley  Plain.  The  leading  features  of  the 
hill  habitat  can  be  said  to  be  (a)  possible  variations  in  aspect;  (6) 
a  relatively  good  water  relation  through  altitude  and  relation  to  higher 
hills  or  mountains;  and  (c)  presence  of  rock  outcrops  with  correspond- 
ing paucity  of  soil  whose  nature  is  determined  by  that  of  the  rocks. 

(3)  The  Mount  Deception  Range  immediately  west  of  Copley. 

(4)  The  washes  or  streams  in  the  hills  and  lowlands. 

Vegetation  of  the  "Alkali"  Plains. 

The  most  important  component  of  the  vegetation  of  the  lowlands, 
particularly  of  the  Copley  Plain,  consists  of  halophytes  in  bewildering 
variety.  These  in  large  part  are  very  similar  in  size  and  in  general 
appearance  and  it  needs  fairly  close  study  to  distinguish  many  of  them. 
They  are  50  cm.  more  or  less  in  height  and  usually  of  a  grayish-green 
color ;  but  some  are  small  annuals  and  some  occur  in  communities  having 
a  common  ancestry,  which  are  of  considerable  extent.  As  a  whole,  the 
halophytic  flora  of  the  far  north  is  of  great  economic  importance,  inas- 
much as  it  constitutes  practically  all  of  the  forage  of  this  vast  region, 
being  thus  the  basis  of  the  pastoral  industry.* 

The  following  species  of  halophytes  were  observed  on  the  Copley 
Plain  or  on  slopes  contiguous  thereto:  Atriplex  spongiosum,  A.  vesi- 
carium,  A.  quinii,  Kochia  pyrmidata,  K.  planifolia,  K.  cannoni, 
K.  villosa,  K.  decaptera,  K.  eriantha,  K.  sedifolia,  Enchylcena  tomentosa, 
Bassia  lanucuspis,  B.  paradoxa,  and  Salicornia  tenuis.  In  addition, 
"salt-loving"  species  of  other  families  were  found,  among  which  were 

♦  In  1912  the  Central,  Lower  North,  and  Upper  North  of  South  Australia  supported  the  follow- 
ing number  of  live  stock:  cattle,  199,727;  horses,  197,139;  sheep,  2,674,856  (Handbook  of  South 
Australia,  1914,  p.  143) ;  there  are  also  several  thousand  camels.  Besides  the  domestic  animala 
which  derive  their  entire  subsistence  from  the  native  flora,  there  should  be  mentioned  the  native 
and  introduced  wild  animals  which  also  subsist  wholly  on  it.  Of  these,  the  most  destructive  are 
the  rabbits.  They  occur  during  favorable  periods  in  countless  numbers  and  work  great  harm  to  a 
very  wide  class  of  vegetation,  including  that  useful  to  sheep,  cattle,  horses,  and  camels. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  69 

Nitraria  schoeberi,  Zygophyllum  crenatum,  Z.  fruticulosum,  and  Z. 
prismatothecum* 

The  vegetation  of  the  Copley  Plain  at  present  is  very  sparse,  in  places 
wanting,  but  in  some  places  it  is  fairly  abundant.  Where  absent,  as 
on  the  higher  portions,  the  dead  stumps  of  shrubs  show  that  in  former 
times  it  also  was  covered  by  plant  growth.  But  in  a  few  small  basins 
without  surface  outlet,  where  there  is  an  excessive  accumulation  of 
salts,  the  edaphic  conditions  do  not  now  and  have  not  in  recent  times 
permitted  the  presence  of  plants.  On  the  lower  and  also  well-drained 
parts  of  the  plain,  on  the  other  hand,  species  of  Atriplex  and  of  Kochia 
especially  occur  in  good  size  and  fair  abundance.  Plate  7c  shows  their 
leading  characteristics.  In  order  to  learn  the  density  of  the  population 
of  saltbushes,  a  census  was  taken  at  the  base  of  Table  Mountain,  about 
a  mile  south  of  Copley,  at  the  upper  limits  of  the  plain  where  it  joins 
the  slope  of  the  hill.  Here  were  Atriplex  and  Kochia,  with  some 
specimens  of  a  small  and  undetermined  grass,  a  geranium,  and  a 
mustard.  The  area  observed  measured  10  meters  square.  In  the  first 
square  40  shrubs  were  counted,  of  which  36  were  Atriplex.  In  the 
second  square,  somewhat  nearer  the  hill,  42  shrubs  were  found,  of  which 
Zygophyllum  fruticulosum  was  the  dominant  form,  the  balance  being 
Salicornia  and  Kochia.  Plate  8a  shows  the  character  of  the  plants  and 
of  the  habitat.  Somewhat  farther  (possibly  200  meters)  on  the  plain 
and  well  away  from  the  slope,  Salicornia  tenuis  was  dominant,  with 
Zygophyllum  present  in  fewer  numbers  than  in  the  second  square.  At 
this  place  there  were  relatively  large  areas  quite  bare  of  halophytes 
other  than  Nitraria  schoeberi,  which  was  growing  on  sandy  hillocks. 
On  the  surrounding  ground,  where  no  perennials  were  found,  there  was 
a  very  dense  covering  of  very  small  plants.  These  were  mainly  an 
annual  species  of  Atriplex,  which  was  largely  in  fruit.  In  such  an 
area,  1  square  meter,  1,200  individuals  were  enumerated. 

One  of  the  characteristic  features  of  the  halophytic  flora  of  the  plain 
is  the  frequent  occurrence  of  such  forms  on  hillocks  of  various  sizes, 
mostly  small,  which  have  been  built  up  around  them  through  wind 
action.  Such  hillocks  were  observed  in  connection  with  species  of 
Zygophyllum,  Atriplex,  Kochia,  and  Nitraria.  In  the  first  three  in- 
stances the  result  seems  to  be  mainly  incidental  to  the  interference 
with  the  wind  flotation  of  the  sand,  but  in  the  last  case  there  is  a  nice 
accommodation  to  the  heaping  sand  on  the  part  of  the  plant  which 
merits  some  attention. 

Nitraria  schoeberi  is  a  low  shrub  of  rather  diffuse  habit.  The  branch- 
lets  are  often  spinose  and  rigid.    The  habit  and  habitat  of  the  plant 

*  The  three  species  of  Zygophyllum,  it  should  be  noted,  are  included  here  doubtfully.  They 
occur  characteristically  on  slopes,  but  also  were  found  at  the  edge  of  the  salt  plain;  hence  their 
inclusion  among  the  halophytes.  It  should  also  be  said  that  certain  species  of  Kochia  especially 
occur  where  the  soil  does  not  appear  to  carry  an  excess  of  salts.  In  general  this  study  does  not 
nndertake  to  distinguish  between  the  species  ab  to  their  toleration  for  salts. 


70  PLANT   HABITS  AND   HABITATS   IN   THE 

are  shown  in  plate  8b.  At  the  climax  of  its  development  a  typical 
Nitraria  hillock  measures  about  3  by  13  meters  in  horizontal  plan. 
The  height  rarely  exceeds  1.5  meters  and  is  usually  somewhat  less. 

The  origin  and  growth  of  a  hillock,  mound,  or  dune  seems  to  be  about 
as  follows:  In  its  earlier  condition  the  seedhng  Nitraria  has  a  well- 
marked  main  stem  with  branches  fairly  well  raised  from  the  surface 
of  the  ground.  In  this  stage  it  does  not  interrupt  the  movement  of 
the  drifting  soil.  Early  in  its  development,  however,  the  lower 
branches  come  to  lie  on  the  surface  of  the  ground  and  thus  provide 
an  obstruction  to  free  movement  of  the  sand.  The  result  is  that  such 
horizontally  disposed  branches  become  covered  by  soil;  they  develop 
roots  and  send  up  shoots  which  in  growing  maintain  their  position 
above  the  accumulating  sand  drift.  Thus  the  plant  adds  to  its  size 
on  every  side ;  the  central  portion  grows  actively  and  keeps  above  the 
surface  of  the  accumulating  soil,  and  the  characteristic  hillock,  ever 
increasing  in  diameter  and  height,  results. 

The  long  diameter  of  the  mounds  seems  to  be  usually  at  right  angles 
to  the  direction  of  the  prevailing  wind,  southeast  and  northwest,  al- 
though there  may  be  exceptions  to  this.  The  "runners"  which  extend 
the  hillock  colony,  as  well  as  characteristic  features  of  such  a  colony, 
are  shown  in  plate  8c. 

When  the  maximum  size  has  been  attained  the  hillock  begins  to 
break  up  in  the  following  way:  Portions  of  the  plant  which  are  about 
centrally  located  die  out,  for  various  reasons,  and  the  soil  about  them 
begins  to  be  removed,  or  possibly  the  converse  is  the  initial  step. 
However  this  may  be,  the  soil  placed  in  the  midst  of  the  dune  is  gradu- 
ally removed  by  wind  action  until  the  original  level  has  been  attained — 
a  process  of  "  base-levehng " — ^and  the  two  ends  are  completely  sepa- 
rated. Thus  two  daughter  mounds  ultimately  result  in  the  natural 
course  of  disintegration  of  any  Nitraria  dune. 

From  observations  on  the  character  of  the  flora  which  occurs  on  and 
around  the  base  of  a  Nitraria  mound,  it  seems  probable  that  the  accu- 
mulated soil  of  the  hillock  does  not  carry  the  large  amount  of  salts 
found  in  the  soil  characteristic  of  the  plain  proper.  Thus  a  greater 
proportion  of  nonhalophytic  annual  growth  is  found  on  the  hillocks 
than  on  the  lower  contiguous  ground. 

Root-Habits  of  Plants  of  the  Plains. 

The  roots  of  typical  annuals  and  of  a  few  perennials  (halophytes) 
which  were  growing  on  the  lowlands  in  the  vicinity  of  Copley  were 
examined.  The  depth  of  soil  in  all  cases  was  greater  than  the  depth 
attained  by  the  roots,  so  that  the  maximum  penetration  took  place. 
The  roots  of  the  perennials  were  for  the  most  part  studied  along  washes 
where  they  had  been  exposed,  although  in  a  few  instances  they  were 
examined  remote  from  drainage  channels  of  whatever  sort.  The  roots 
of  annuals  were  seen  on  the  open  plain,  but  mostly  where  diminutive 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  71 

hollows  made  possible  relatively  favorable  water  conditions,  with 
results  which  can  be  briefly  given. 

In  one  place  the  roots  of  several  annuals,  mainly  of  species  I  did  not 
know,  were  examined.  The  shoots  were  2  to  7  cm.  long  and  for  the 
most  part  either  in  flower  or  in  fruit,  and  therefore  fully  matured 
specimens.  A  cruciferous  species  had  a  tap-root  which  varied  in  length 
from  4  to  8  cm.  Another  species,  with  a  rosette,  had  a  prominent 
tap-root  7  to  9  cm.  long.  Of  all  the  annuals  seen  at  this  place  none 
had  roots  which  penetrated  over  12  cm. 

In  another  locality,  about  2  miles  east  of  Copley,  but  on  a  sloping 
plain,  the  roots  of  several  annuals  were  dug  up.  Among  these  were 
several  specimens  of  Zygophyllum  crenatum.  In  specimen  a  the  shoot 
consisted  of  4  leaves  and  was  6  cm.  long,  and  the  tap-root  was  found 
to  be  8  cm.  in  length.  It  was  little  branched.  In  specimen  h  the  shoot 
bore  6  short  leaves  and  was  4  cm.  in  length.  The  tap-root  was  over 
13.5  cm.  long.    Specimen  c  had  a  tap-root  over  8.5  cm.  in  length. 

Roots  of  Geranium  pilosum,  which  is  one  of  the  most  common  annuals 
on  the  plain,  and  which  was  growing  abundantly  near  the  Zygophyllum, 
were  also  examined.  In  specimen  a  the  small  rosette  had  7  leaves 
and  flowers  had  been  formed.  The  leading  root  was  a  tap-root,  but 
this  bore  numerous  fine  laterals.  It  penetrated  to  a  depth  of  more  than 
8.5  cm.  In  specimen  b  the  shoot  was  somewhat  larger  and  the  tap- 
root was  traced  to  a  depth  of  over  11  cm.  In  another  situation,  where 
the  plain  was  in  part  bare  but  where  there  were  also  slight  and  in- 
conspicuous hollows,  there  was  a  sparse  growth  of  annuals.  These 
were  of  various  species,  including  an  undetermined  grass  about  3  cm. 
high,  a  species  of  Geranium,  a  Zygophyllum,  and  some  crucifers.  As 
a  rule  the  shoots  of  the  annuals,  which  were  fully  matured,  did  not 
exceed  4  cm.  in  height.  Although  there  was  found  to  be  a  certain 
specific  difference  in  the  root-systems  of  these  plants,  it  was  learned 
that  in  no  case  did  the  penetration  exceed  13  cm.  and  it  was  mostly 
less.  In  the  case  of  the  Zygophyllum,  prominent  laterals  8  cm.  long, 
more  or  less,  were  found. 

As  a  result  of  the  observations  on  the  winter  annuals  of  the  Copley 
Plain,  it  can  be  said  that,  even  under  such  relatively  favorable  local 
water  relations,  the  roots  do  not  penetrate  the  ground  over  10  to  13 
cm.  and  for  the  most  part  they  lie  closer  to  the  surface  than  this. 

The  roots  of  species  of  Atriplex  and  of  Kochia,  which  were  also 
situated  on  the  Copley  Plain,  were  examined  in  several  specimens, 
and  a  certain  parallelism  in  development  was  noted,  similar  to  the 
development  of  the  root-systems  of  most  perennials,  other  than 
halophytes,  which  were  seen.  One  of  the  features  of  the  plain  referred 
to  is  the  presence  of  various  dead  perennials,  mainly  halophytes. 
Whatever  may  have  been  the  cause  of  the  death  of  the  plants,  it  was 
noted  that  the  root-system  remained  almost  intact.     The  roots  of 


72  PLANT   HABITS   AND   HABITATS   IN   THE 

such  dead  specimens  had  certain  points  of  interest.  It  was  found 
that  soil  no  longer  remained  around  the  base  of  the  halophyte  when 
dead  as  it  does  around  the  hving  plant,  but  it  is  removed  from  the 
root-crown,  exposing  the  origins  of  the  superficial  roots  very  completely. 
In  every  instance  the  dead  root-crown  is  surrounded  by  a  radiating 
circle  of  small  roots  which  start  away  in  a  fairly  horizontal  direction. 
In  one  plant  of  undetermined  species,  where  the  superficial  roots 
were  exposed  in  the  manner  indicated,  23  were  counted,  all  very  close 
to  the  surface,  but  3  or  4  were  found  more  deeply  placed. 

Living  plants  mostly  were  studied  and  the  results,  as  above  sug- 
gested, were  very  uniform.  A  Kochia  which  was  growing  on  the  plain 
at  some  distance  from  any  wash  was  carefully  removed  from  the  ground. 
A  tap-root  which  penetrated  39  cm.  into  the  soil  was  seen  to  be  fairly 
moist.  All  of  the  laterals,  of  which  there  were  several,  arose  at  a  depth 
of  about  10  cm.  from  the  surface  and  were  traced  more  than  60  cm. 
from  their  place  of  origin.  A  species  of  Atriplex,  situated  by  the  side 
of  a  small  wash  and  not  far  from  the  Kochia  just  mentioned,  was 
found  to  have  a  prominent  tap-root  and  prominent  laterals  which  ran 
in  a  fairly  horizontal  direction,  and  not  far  beneath  the  surface.  A 
species  of  Salicornia,  growing  close  by,  had  a  root  which  penetrated 
to  a  depth  of  15  cm.  and  then,  turning  sharply,  ran  horizontally.  Sev- 
eral large  horizontal  roots  arose  within  10  cm.  of  the  surface  of  the 
ground  and  many  small  laterals  took  their  origin  at  about  half  that 
depth.  So  far  as  this  species  is  concerned,  therefore,  the  laterals 
constitute  a  very  prominent  feature  of  the  root-system  as  a  whole. 
That  a  recent  rain  of  0.21  inch  penetrated  to  the  roots  of  this  species 
was  evident  from  the  fact  that  the  branches  and  leaves  were  turgid. 

Of  the  root  exposures,  however,  the  best  were  found  along  a  recent 
wash  to  the  north  of  Table  Mountain,  where  a  small  box  canyon, 
about  100  meters  in  length  by  half  that  width,  had  been  eroded. 
The  sides  were  vertical  and  the  walls  about  1.2  meters  high.  The  wash 
ran  through  a  small  plain  on  which  were  Atriplex  and  Kochia  mainly, 
with  Atriplex  sp.  dominant.  The  roots  of  several  plants  were  partly 
exposed  and  were  observed.  Since  the  roots  of  all  were  about  the 
same,  a  description  of  those  of  one  will  be  sufficient.  In  this  specimen 
the  shoot  was  only  in  part  hving  and  it  was  apparent  that  a  portion 
had  been  removed.  Of  the  roots,  it  was  found  that  3  fairly  large  ones, 
representing  tap-roots,  went  straight  down  over  1  meter.  Several  took 
their  origin  from  these  vertical  roots  just  beneath  the  surface  of  the 
soil  and  ran  in  a  horizontal  direction,  about  2  cm.  beneath  the  surface, 
to  the  base  of  a  neighboring  Atriplex,  about  1.5  meter  distant.  The 
vertical  roots  gave  off  small  and  relatively  unimportant  branches  at  a 
depth  of  about  30  cm.  The  superficial  horizontal  roots  bore  numerous 
filamentous  roots  and  such  roots  were  seen  on  the  most  superficial  of  the 
other  laterals.    Such  filamentous  roots  correspond  to  the  "deciduous" 


ARID    PORTIONS    OF    SOUTH   AUSTRALIA.  73 

rootlets  which  have  been  seen  to  occur  on  similarly  placed  superficial 
laterals  of  several  species  in  the  Tucson,  Arizona,  region. 

The  roots  of  perennials  growing  on  the  Copley  Plain,  and  described 
in  the  foregoing  paragraph,  are  all  either  sharply  vertical  or  as  sharply 
horizontal  in  position.  It  is  probable,  from  the  la,rge  number  of  ob- 
servations, that  this  is  the  usual  condition.  However,  an  exception 
was  found  by  a  wash  on  the  edge  of  the  plain,  where  the  soil  is  fairly 
coarse  and  the  bank  is  about  2  meters  high.  Here  an  undetermined 
halophytic  shrub  of  small  stature  had  a  root-system  which  was  unlike 
that  above  described.  In  this  instance  there  was  a  brush  of  roots, 
without  the  sharp  differentiation  into  the  vertical  and  horizontal 
members  as  elsewhere  observed.  This  condition  is  probably  attributa- 
ble to  the  fact  that  the  soil  at  the  place  is  relatively  coarse,  permitting 
a  deeper  penetration  of  the  rain  and  better  conditions  of  aeration 
than  would  more  commonly  be  the  case. 

Vegetation  of  the  Low  Hills  and  Slopes. 

The  lower  hills  and  slopes  and  the  slopes  of  the  higher  hills  are 
usually  well  covered  with  a  perennial  vegetation.  Although  some  of 
it  is  of  the  halophytic  type,  it  is  largely  composed  of  sclerophyllous 
shrubs,  fairly  uniform  in  appearance  and  generally  of  a  relatively 
small  size.  The  hill  vegetation  is  so  varied  in  species  that  it  would 
require  a  much  closer  study  than  the  present  one  to  describe  it  at  all 
accurately,  as  well  as  the  aid  of  a  large-scale  contour  map  showing 
the  leading  geological  features.  Such,  unfortunately,  appears  to  be 
wanting.  Certain  leading  characteristics,  however,  can  be  presented 
as  a  preliminary  study.  Possibly  the  most  striking  single  feature  of 
the  hill  perennial  flora  is  the  frequent  segregation  of  species,  so  that  a 
relatively  large  area  may  be  populated  by  a  single  one  to  the  exclusion 
of  all  others.  This  was  noted  again  and  again.  Although  there  are 
many  species  of  perennial  habit  on  the  hills,  it  is  probably  true  that  the 
most  typical  belong  to  two  genera,  Cassia  and  Eremophila.  It  will 
therefore  probably  convey  the  right  impression  if  the  vegetation  of 
the  hills  was  defined  as  the  Cassia-Eremophila  community.  Following 
are  some  of  the  most  conspicuous  species  of  the  low  hills  and  slopes: 

Eremophila  brownii.  Eucalyptus  oleosa.  Atriplex  vesicarium. 

E.  freelingii.  Cassia  eremophila.  Bassia  lanicuspis. 

E.  oppositifolia  (plate  8c).  C.  sturtii.  Hakea  leucoptera. 

E.  latrobei.  Myoporum  platycarpum.  Nicotiana  suaveolens. 
Zygophyllum  fruticulosum.  Acacia  sentis.  Petalostylis  labicheoides. 
Z.  crenatum.  A.  aneura.  Solanum  illipticum. 

Z.  prismatothecum.  Cheilanthes  tenuifolia.  Menkea  australis. 

Pholidia  scoparia.  Kochia  planifolia.  Pimelea  microcephala. 

Fusanus  acuminatus.  K.  sedifolia.  Trichinium  incanum. 

F.  spicatus.  Euchylaena  tomentosa.  Casuarina  lepidophloia. 


74  PLANT   HABITS   AND    HABITATS   IN  THE 

Mono-Specific  Communities. 

Although  the  hill-slope  habitat  is  here  treated  as  a  single  unit,  it  is 
nevertheless  far  from  uniform.  However,  as  this  habitat  is  well 
drained  and  hence  the  soil  is  well  aerated,  with  relatively  good  water 
relations  and  various  aspects,  it  may  be  proper  to  group  the  different 
slopes  into  one  habitat.  One  of  the  features  of  the  habitat  is  that  any 
one  element,  for  example  the  slope  of  a  hill,  is  cf  relatively  large  area,  so 
that  the  environmental  conditions  of  the  particular  area  are  correspond- 
ingly of  relatively  wide  extent.  This  uniformity  of  environmental 
conditions  extending  over  a  relatively  wide  area  is  doubtless  responsible 
for  the  frequent  occurrence  of  a  single  species  only,  particularly  of 
perennials,  thoughout  such  an  area.  Thus  it  happens  that  mono- 
specific communities  are  common  in  the  Copley  region.  Some  of  these 
will  be  mentioned  here.  The  most  conspicuous  are  those  of  various 
species  of  Eremophila.  Of  these,  the  ones  along  or  accessible  from  the 
Mount  Series  road  may  be  considered  typical  and  need  only  be  de- 
scribed. 

To  the  east  of  the  village  the  Copley  Plain  pushes  into  the  hills, 
forming  a  bay-like  area,  Vv'ith  hills  to  the  south,  ending  at  the  west  in 
Table  Mountain  and  lower  hills  on  the  north.  The  plain  rises  about 
1.5  miles  from  the  village  and  insensibly  merges  into  gentle  slopes  which 
descend  from  the  hills  on  the  south.  At  the  place  in  mind  there  is  a 
considerable  outcropping  of  slate  or  shale.  With  its  northern  aspect, 
the  habitat  is  relatively  warm  and  is  subject  to  the  north  winds,  which 
at  times  are  hot  and  dry.  On  this  slope  occurs  Eremophila  freeUngii, 
solely  among  perennials.  This  is  a  shrub  about  1.5  meters  in  height, 
with  an  open  habit  of  growth.  The  leaves  are  numerous  and  fairly 
crowded  towards  the  ends  of  the  branches  (plate  9a).  They  are  of 
leathery  texture,  about  3  cm.  in  length,  and  somewhat  viscid.  In 
the  middle  of  July,  when  the  area  was  first  studied,  they  bore  large 
numbers  of  lavender-colored  flowers.  No  measurements  were  made 
nor  computations  of  the  populations  per  unit  area.  It  can  be  seen 
from  plate  10b,  however,  that  the  shrubs  occur  but  sparsely.  An- 
other area,  in  which  E.  freeUngii  occurs  to  the  exclusion  of  other  species 
of  perennials,  is  by  the  Mount  Serle  road  and  about  5  miles  east  of 
Copley.  Here  are  rounded  slate  hills  also  and  the  conditions  are 
otherwise  much  as  at  the  habitat  just  described  (plate  9c). 

An  additional  mono-specific  community  observed  was  that  of 
Pholidia  (formerly  Eremophila)  scoparia,  which  was  not  far  from  the 
habitat  last  mentioned.  It  was  different,  however,  in  that  the  slope 
has  a  southern  aspect  and  is  somewhat  less  steep.  Probably  the 
water  conditions  are  somewhat  more  favorable.  Pholidia  scoparia  is 
rather  strict  in  habit,  "broom-like,"  in  fact,  and  has  small  leaves  closely 
appressed  to  the  branches,  as  shown  in  plate  9c.  The  shrubs  have  a 
canopy  top  and  are  1.5  to  2  meters  in  height.    Where  they  constitute 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  75 

the  sole  species,  as  at  the  habitat  mentioned,  they  form  one  of  the 
most  striking  conamunities  of  the  whole  region  (plate  10c). 

A  mono-specific  community  of  quite  a  different  character  was  ob- 
served on  the  upper  slopes  of  hills  leading  up  to  the  eastern  summits  of 
the  Mount  Deception  Range,  about  4  miles  to  the  west  of  Copley. 
When  viewed  from  the  plain,  there  appeared  at  this  place  a  bright- 
green  area,  as  of  a  grassy  field.  When  it  was  reached,  however,  by  the 
way  of  the  lower  hills,  it  was  found  to  consist  wholly  of  Zygophyllum 
crenatum,  a  low,  spreading  annual.  There  was  no  other  species  of 
any  sort  over  the  rather  large  area,  possibly  of  several  acres. 

Among  other  species,  which  occur  in  large  numbers  to  the  exclusion 
of  others,  is  Cassia  sturtii.  This  is  a  somewhat  diffuse  shrub  about 
1.5  meters  high.  It  appears  to  have  been  much  more  abundant  in 
former  times  in  the  vicinity  of  Copley,  if  one  can  judge  from  the 
large  areas  which  now  are  covered  with  specimens  no  longer  living,  as 
on  certain  slopes  of  the  Mount  Deception  Range.  At  present,  how- 
ever, it  is  common  enough.  Frequently,  as  among  the  rounded  hills 
along  the  Mount  Series  road  about  5  miles  east  of  the  village,  it  forms 
fairly  large  communities  (plate  10a).  It  seems  to  be  restricted  to  hills 
and  slopes. 

Another  example  of  a  mono-specific  community  is  that  of  Kochia 
sedifolia,  which,  unlike  so  many  of  the  family,  appears  not  to  tolerate 
a  large  amount  of  salts  in  tha  soil,  so  that  possibly  it  may  not  be  con- 
sidered a  strict  halophyte.  It  occurs  on  slopes  which  are  often,  but 
not  always,  somewhat  above  the  plain.  The  situation  of  the  habitat 
to  be  described  is  along  the  Yudnamutana  road,  about  2  miles  north- 
east of  Copley,  where  an  intermittent  stream,  making  its  way  across  a 
slope  from  hills  farther  east,  has  cut  a  fairly  deep  gorge.  To  the  south 
of  the  edge  of  the  latter  the  slope  dips  gently  to  the  Copley  Plain. 
The  population  is  fairly  sparse,  as  the  habitat  shows  (plate  7c).  The 
individuals  are  about  50  cm.  high  and  of  a  very  close,  compact  growth- 
habit.  The  species  occurs  to  the  exclusion  of  others  over  an  area 
many  acres  in  extent. 

Zygophyllum  fruiiculosum  is  another  species  which  may  occur  solely 
in  a  habitat.  This  small  shrub,  of  a  lax  growth-habit,  grows  on  the 
lower  slopes  of  the  Mount  of  Light  as  well  as  on  nearby  slopes  to  the 
exclusion  of  other  species  of  perennials.  The  habit  and  distribution 
of  the  species,  as  well  as  the  ch^^racter  of  the  habitat,  are  fairly  well 
shown  in  plate  lie. 

An  additional  species,  which  occurs  with  little  or  possibly  no  acl 
mixture  of  other  species  in  certain  areas,  is  Eucalyptus  oleosa.  This 
is  one  of  the  "mallees."  Although  the  mallee  does  not  form  a 
conspicuous  member  of  the  plant  community  at  Copley,  it  is  to  be 
found  scattered  along  the  washes,  and  at  a  place  about  4  miles  west  of 
the  village  and  in  the  Mount  Deception  Range  a  mallee  thicket  haa 


76  PLANT   HABITS    AND   HABITATS   IN   THE 

been  formed.  The  species  has  a  heavy  root-crown  and  a  thickened 
stem-base,  from  which  numerous  branches  arise.  The  entire  aspect 
of  the  species  is  shrub-like,  with  the  "canopy"  top  so  common  among 
AustraUan  shrubs  and  trees. 

Isolated  Species  and  Mixed  Communities. 

Should  the  vegetation  of  the  Copley  region  be  studied  from  the 
standpoint  of  its  distribution,  it  would  be  found  that  all  gradations 
exist  between  the  mono-specific  communities  above  sketched  and 
geographically  isolated  individuals.  As  a  matter  of  fact,  possibly 
most  of  the  species  occur  mingled  in  this  manner.  Whether  such  small 
communities  or  isolated  individuals  represent  recent  introductions 
or  survivals  from  populous  mixed  communities  are  matters  of  interest, 
but  this  study  throws  no  light  on  the  problem.  It  is  evident  that  the 
controlling  factor  of  the  hill-slope  flora  is  the  single  one  of  moisture 
and  that  it  is  apparently  a  fortuitous  mingling  of  mostly  unrelated 
elements.  This  is  in  sharp  contrast  to  the  flora  of  many  species  of  the 
Copley  plain,  which  is  bound  by  edaphic  ties.  In  other  words,  the 
conditions  noted  are  the  usual  ones  controlling  the  plant  distribution 
in  an  arid  or  semi-arid  region. 

It  is  not  especially  unusual  to  find  a  single  species  of  woody  perennials 
represented  in  any  area  by  one  specimen  only.  For  example,  one  or 
two  specimens  only  of  Hakea  leucoptera  occur  on  the  top  of  Table 
Mountain  (plate  11  a),  although  there  is  a  small  colony  of  about  20 
widely  separated  individuals  on  low  slopes  at  the  head  of  a  draw  at 
the  east  base  of  Mount  Deception  Range  west  of  Copley.  It  was  not 
seen  apart  from  these  two  situations.  At  Copley  the  species  has  the 
habit  of  a  small  tree,  about  5  meters  high,  with  a  pronounced  canopy- 
shaped  crown.  The  leaves  are  needle-like  (plate  12d)  and  the  whole 
appearance  of  the  species  is  as  one  well  adjusted  to  very  arid  condi- 
tions. It  is  one  of  the  species  which  has  probably  suffered  little  by 
the  advent  of  the  white  man  and  his  varied  activities.  It  is  not  eaten 
by  his  animals  or  used  by  him  as  a  fuel.  For  these  reasons  the  oc- 
currence of  the  species  as  to  its  distribution  in  the  Copley  region 
probably  represents  its  reaction  to  the  physical  environment  only. 
Such  a  remark  might  also  be  made  regarding  smaller  woody  peren- 
nials, as  the  Eremophilas  and  Cassias. 

Another  woody  perennial  which  occurs  sparingly  is  Petalostylis 
labicheoides.  This  species  was  found  at  the  south  and  west  base  of 
Table  Mountain,  in  a  straggling  group  or  two  of  few  individuals.  It 
was  seen  in  no  other  place.  The  shrub  has  a  very  striking  appearance, 
but  imperfectly  shown  in  plate  12,  a  and  c.  Several  branches  of  ap- 
proximately equal  length  are  fairly  well  clothed  with  compound  leaves 
which  carry  15  to  31  leaflets.  Thus  the  leaf-area  is  large,  although  the 
leaflets  are  rather  small. 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  77 

Among  other  species  of  the  hill-slope  habitat  which  occur  rarely  or 
scatteringly,  mention  need  be  made  of  two  or  three  additional  ones 
only.  Thus,  Cheilanthes  ienuifoHa  was  found  only  among  rocks, 
south  surfaces,  on  the  northern  slope  of  Table  Mountain.  Casuarina 
lepidophloia  occurs  in  small  numbers  around  the  south  and  west  base 
of  Table  Mountain  (plates  11b  and  12b),  and  also  in  few  numbers 
among  the  low  hills  on  the  Mount  Series  road.  In  other  places,  as  on 
the  top  of  Table  Mountain,  the  species  occurs  sparingly.  This  species 
forms  a  small  tree  in  the  vicinity  of  Copley  and  is  of  some  economic 
use,  making  it  probable  that  the  number  of  individuals  is  very  much 
less  now  than  in  earlier  times.  It  is  to  be  questioned,  however,  whether 
it  ever  occurred  so  abundantly  at  Copley  as  to  constitute  a  pure  com- 
munity, as  at  Quorn,  for  example. 

An  additional  species  which  occurs  but  sparingly  at  Copley  is 
Pimelea  microcephala.  Two  specimens  of  this  small  shrub  were  found 
at  the  eastern  base  of  the  Mount  Deception  Range  and  in  the  same 
habitat  as  Hakea  leucoptera.  It  occurs  in  certain  other  places  also, 
as  to  the  south  of  Table  Mountain. 

Vegetation  of  the  Washes. 

There  is  no  sharp  distinction  between  the  plants  of  the  hill-slope 
habitat  and  that  of  either  the  plain  or  of  other  portions  of  lowlands, 
provided  the  drainage  is  good.  Thus  there  are  lines  of  stress  between 
contiguous  habitats  where  the  species  most  characteristic  of  each  are 
more  or  less  mingled.  Some  instances  of  invasion  may  be  found,  but 
these  appear  to  be  rather  uncommon.  Inasmuch  as  the  water  rela- 
tions of  the  washes  of  whatever  kind  are  particularly  favorable,  this 
fact  is  reflected  in  the  vegetation  growing  in  them.  Thus,  species 
with  large  water  requirements  may  be  found  in  such  a  habitat,  and  as 
a  general  thing,  although  not  without  exceptions,  such  forms  have  a 
relatively  large  transpiring  surface,  may  be  of  good  size,  and  may 
occur  in  abundance. 

One  of  the  most  characteristic  trees  of  the  washes  is  the  red  gum. 
Eucalyptus  rostrata.  This  becomes  a  fair-sized  tree  whose  habit  of 
growth  is  illustrated  in  plate  13c.  In  places,  as  on  Leigh's  Creek  near 
Copley,  the  red  gum  is  confined  to  the  floor  of  the  wash.  Here  the 
bank  is  about  5  meters  high  and  has  all  of  the  physical  characteristics 
of  the  plain  of  which  it  is  a  part.  Somewhat  farther  up  the  same  wash, 
however,  the  transition  from  flood-plain  to  the  adjacent  higher  ground 
is  gradual  and  the  plant  communities  characteristic  of  wash  and  plain 
are  more  or  less  mingled.  Smaller  contributing  washes,  whose  depth 
may  be  little  if  any  over  a  meter  and  whose  width  may  be  no  greater, 
also  carry  the  species.  Such  small  washes  are  marked  by  a  "single 
file"  of  the  gums  crossing  the  plain.  The  same  wash  entering  the  hills 
to  the  east  of  Copley  is,  with  its  smaller  branches,  likewise  populated 
with  the  gums.     It  is  apparent,  therefore,  that  the  species  is  very 


78  PLANT   HABITS   AND   HABITATS   IN   THE 

closely  and  directly  dependent  on  a  relatively  good  water-supply. 
It  would  be  impossible  to  judge  the  earlier  distribution  and  frequency 
of  the  species  from  its  occurrence  at  present,  owing  to  the  past  as  well 
as  the  present  demands  of  the  white  population  for  its  use  in  various 
domestic  purposes.  However  that  may  be,  owing  to  the  close  depend- 
ence of  the  species  on  a  good  water-supply  and  to  its  not  being  very 
tolerant  of  an  excess  of  salts  in  the  soil  solution,  and,  further,  owing 
to  the  fact  that  the  physiogi'aphic  conditions  are  by  and  of  themselves 
much  restricted,  it  is  hardly  to  be  supposed  that  the  species  at  any  time 
had  a  distribution  different  from  what  it  has  now,  even  if  the  number 
of  individuals  may  have  been  greater. 

Among  the  other  woody  perennials  found  in  and  along  the  washes 
are  Melaleuca  glomerata  and  M.  parviflora.  Although  these  species 
are  confined  to  the  washes,  they  are  not  generally  distributed  along 
them,  as  is  the  case  of  the  red  gum,  but  are  segregated  into  isolated 
masses.  Both  species,  for  example,  are  to  be  found  on  the  flood- 
plain  of  Leigh's  Creek  at  a  place  near  the  Myrtle  Springs  road  and 
about  2  miles  from  Copley,  and  also  in  a  small  wash  not  far  from  the 
Yudnamutana  road,  about  3  miles  north  of  the  town.  M.  parviflora 
is  a  small  tree  (plates  13b  and  15a)  and  is  said  to  be  tolerant  of  an  excess 
of  salts  in  the  soil  solution,  and  thus  to  be  an  ''indicator"  of  brackish 
water.  M.  glomerata,  on  the  other  hand,  is  said  to  be  an  "indicator" 
of  fresh  water.  However  that  may  be,  the  two  species  are  closely 
associated  in  the  two  habitats  above  referred  to.  M.  glomerata  is  a 
large  shrub  (plates  13a  and  15d)  and  under  conditions  such  as  occur 
along  the  Myrtle  Springs  road  may  form  a  dense,  jungle-like  growth 
with  semi-prostrate  stems,  unique  in  this  regard  and  different  from 
most  species  of  a  semi-arid  region.  In  both  species  the  leaves  are  small, 
almost  needle-like,  but  numerous,  and  hence  the  transpiration  surface 
of  any  individual  is  large. 

Of  other  species  belonging  to  the  washes,  there  may  be  mentioned 
certain  Eremophilas,  some  of  which  are  wholly  confined  to  drainage 
channels.  Of  these,  the  most  pronounced,  so  far  as  the  characteristic 
just  mentioned  is  concerned,  is  E.  alternifolia  (plate  14a).  Whenever 
in  the  Copley  vicinity  an  Eremophila  was  found  along  a  drainage 
channel,  however  smaU,  as  a  slight  depression  on  a  slope,  it  was  nearly 
always  of  this  species.  In  spite  of  the  fact  that  (as  plate  15b  shows) 
the  leaves  are  fairly  small,  it  seems  necessary  for  the  species  to  have 
much  better  water  relations  than  any  other  of  the  genus  occurring 
in  this  vicinity.  Eremophila  latrobei  is  a  small  tree;  it  was  found  in  a 
small  wash  near  the  Yudnamutana  road  and  nowhere  else.  Ere- 
mophila longifolia  occurs  in  the  same  locality  and  elsewhere,  but  is 
not  common.  It  also  is  a  small  tree.  The  habit  of  the  species  and  of 
the  leaf  is  shown  in  plates  14b  and  16a. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  79 

Of  other  species  found  only  in  or  along  washes,  Acacia  varians, 
''native  willow,"  becomes  a  fairly  large  tree  with  drooping  willow-Uke 
habit  (plate  15c).  This  species  does  not  appear  to  be  very  common. 
A.  sentis  and  A.  tetragonophylla  are  confined  to  bottoms  by  drainage 
channels,  or  to  such  channels.  The  former  is  not  abundant,  but  the 
latter  forms  small  thickets  which  are  nearly  impenetrable,  hence  the 
local  name  "dead  finish,"  not  alone  because  of  the  abundance  of  the 
individuals,  but  also  because  of  the  short  and  sharply  pointed  phyllodia 
(plate  16,  B  and  c).  Casuarina  lepidophloia  occurs  along  bottoms  con- 
tiguous to  washes  not  far  from  the  one  along  which  Acacia  varians 
was  found.  Senecio  magnificus  occurs  only  where  the  water  relations 
are  relatively  good,  as  in  or  along  washes. 

Of  other  species  confined  to  washes,  or  to  their  inmiediate  vicinity, 
Heterodendrum  olecefolium,  Myoporum  platycarpum  (plate  17b),  and 
Jasminum  lineare,  all  small  trees,  may  be  mentioned.  Although  the 
leaves  of  all  are  relatively  large,  those  of  the  first  named  are  the  largest 
and,  as  will  appear  below,  possibly  rank  next  to  those  of  Eucalyptus 
oleosa  in  size,  indicative  of  an  adjustment  to  relatively  favorable  water 
conditions. 

Parasitic  Phanerogams, 

The  flowering  parasites  constitute  a  very  conspicuous  portion  of 
flora  of  the  Copley  region.  They  represent  two  families,  the  Loran- 
thacese  and  the  Santalacese.  Of  the  former,  Loranthus  exocarpi,  L. 
linearifolius,  and  L.  quandang,  and  of  the  latter  family,  Fusanus  acumi- 
natus  and  F.  spicatus  were  seen.  The  mistletoes  are  of  very  general 
occurrence,  but  the  sandal-woods  occur  much  more  sparsely. 

Loranthus  exocarpi  is  the  most  commonly  met  of  the  mistletoes.  It  is 
to  be  found  on  a  relatively  large  number  of  hosts,  among  which  were 
seen  Eremophila  brownii  (plate  17d),  E.  longifolia,  Fusanus  acuminatus, 
Acacia  sentis  (plate  17c),  Melaleuca  glomerata,  and  Myoporum  platy- 
carpum (plate  18c).  Loranthus  linearifolius  was  found  on  Acacia 
tetragonophylla  (plate  18b),  and  L.  quandang  was  seen  on  Acacia 
aneura.  Of  these  species,  only  L.  exocarpi  on  Eremophila  longifolia 
and  L.  quandang  on  Acacia  aneura  (plate  18a),  the  "mulga,"  were  seen 
to  be  in  harmful  abundance.  In  the  latter  instance,  especially,  the 
parasitic  relation  is  said  to  terminate  fatally  for  the  host  in  every 
instance  and  within  two  years  or  more  following  infection.  A  striking 
peculiarity  of  the  leaves  of  certain  of  the  parasitic  couples  is  the  strong 
superficial  resemblance  which  they  hold. 

The  sandal-woods  are  small  evergreen  trees  and  occur  rather  spar- 
ingly in  the  hill-slope  habitat  and  apparently  nowhere  else.  The 
fewness  in  the  number  of  individuals  is  in  part  attributable  to  demands 
of  various  kinds  which  are  made  on  them.  They  are  a  source  of  fuel 
and  also  are  attacked  by  animals  which  devour  the  young  branches 
and  leaves.  The  fruits  of  one  of  them,  the  "native  peach,"  F.  acumi- 
natus, are  used  as  food  to  a  certain  extent  by  dwellers  in  the  region. 


80  PLANT   HABITS   AND   HABITATS   IN   THE 

Root-Habits  of  Plants  of  the  Washes. 

A  few  root  exposures  were  found  along  different  washes,  where  the 
erosion  of  the  soil  left  them  more  or  less  in  place.  The  leading  results 
of  the  observations  on  them  can  be  briefly  given. 

Pholidia  scoparia  has  a  large  development  of  roots  which  take  their 
origin  near  the  surface  of  the  soil,  and  at  less  than  1  meter  from  the 
main  root  they  attain  to  a  depth  of  approximately  40  cm.  and  maintain 
this  depth  for  an  undetermined  distance.  There  also  is  a  well-marked 
tap-root.  Essentially  the  same  condition  was  seen  in  Eremophila 
freelingii,  which  was  growing  on  the  edge  of  a  wash  whose  bank  was 
over  3  meters  high.  In  this  case,  however,  numerous  radiating  roots 
were  seen  and  no  tap-root.  The  roots  of  unknown  shrubs  which  were 
growing  along  a  smaller  wash  had  roots  of  the  same  general  type  as  that 
given  above  for  Pholidia.  An  undetermined  species  of  Acacia  was 
found  to  have  two  prominent  roots  which  were  superficially  placed; 
the  balance  of  the  roots  were  not  seen.  The  most  deeply  penetrating 
tap-toot  found  was  of  an  unknown  Atriplex,  which  went  to  a  depth  of 
about  2  meters.  This  species  also  had  roots  horizontally  placed. 
By  a  wash  leading  down  from  the  Mount  Deception  Range  there  is  a 
small  straggling  grove  of  Eucalyptus  oleosa  where  a  few  roots  are  ex- 
posed. As  the  bank  was  not  a  high  one  the  exposure  was  not  extensive. 
It  showed,  however,  the  swollen  stem-base  and  enlarged  root-crown, 
"mallee"  characters,  and  the  origin  of  the  main  roots  (plate  19b). 

It  appears  from  these  observations  that  the  root-systems  of  peren- 
nials of  the  washes  and  hill-slopes,  with  the  possible  exception  of  that  of 
Pholidia  scoparia,  consist  of  a  deeply  penetrating  portion  and  a  super- 
ficial portion  which  extend  in  a  horizontal  direction.  Obhgate  deeply 
penetrating  or  obligate  superficial  root-systems  probably  do  not  occur. 

Leaf-Foem  and  Leaf-Sizes. 

The  leaves  of  all  of  the  perennials  observed  at  Copley  are  coriaceous, 
and  although  they  vary  considerably  in  size  they  have  a  certain  monot- 
ony in  outline.  A  few  of  the  species  have  linear  leaves,  or  phyllodia, 
and  these  may  be  greatly  elongated  or  they  may  be  short  and  almost 
spine-like.  The  widest  as  well  as  the  longest  leaves  were  those  of 
Eucalyptus  rostrata,  which  may  be  characterized  as  being  narrow 
elongate.  Thus,  except  for  the  juvenile  leaves  of  this  species,  there 
appears  to  be  no  perennial  in  the  region  with  leaves  that  are  even 
ovate,  not  to  mention  the  wider  possible  forms. 

A  detailed  account  of  the  sizes  and  forms  of  leaves  will  be  given  in  a 
separate  section.  Here  it  will  be  sufficient  to  present  a  summary  show- 
ing the  relative  sizes  of  the  leaves  of  several  different  species.  The 
leaves  of  Eremophila  alternifolia  are  given  a  value  of  1 ;  from  this  as  the 
base,  the  relative  size  (area)  of  the  leaves  of  several  species  is  as  fol- 
lows: Acacia  aneura,  1.3;  Eremophila  hrownii,  2;  Myoporum  platycar- 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  81 

pum,  5;  Fusanus  acuminatus,  7;  Fusanus  spicatus,  13;  Acacia  varians, 
15;  Eucalyptus  rostrata,  20  to  26.  As  this  is  a  portion  only  of  the 
species  observed,  no  safe  conclusion  can  be  drawn  from  the  relation 
above  them.  It  is  of  interest  to  note  the  relatively  large  leaf-area  of 
Eucalyptus  rostrata  and  ^caaa  varians,  which  are  strictly  confined  to  the 
habitat  of  the  washes.  But  the  complete  exposition  of  leaf-sizes  of 
such  a  habitat  as  the  wash,  however,  would  show  great  variation. 
Thus  Eremophila  alternifolia  is  confined,  and  quite  strictly  so,  to  this 
habitat,  and  it  has  the  smallest  leaves  measured.  It  should  be  said, 
in  this  connection,  that  a  great  reduction  in  the  transpiring  surface, 
even  to  a  condition  of  total  aphylly,  is  not  uncommon  in  species  with 
large  water-requirement.  The  opposite  condition,  however,  namely, 
the  occurrence  of  large-leaved  species  in  dry  habitats,  does  not  take 
place.  Therefore,  the  general  rule  can  probably  be  said  to  hold,  that 
there  is  a  direct  relation  between  leaf -size  (or  transpiration  surface)  and 
water-relation,  at  least  in  an  arid  region  such  as  that  about  Copley. 

VEGETATION  OF  SOUTHWESTERN  SOUTH  AUSTRALIA. 

In  the  brief  discussion  to  follow,  on  the  plants  of  the  southwestern 
portion  of  the  state  and  on  their  environment,  the  vegetation  of  only 
three  stations  along  the  line  of  the  trans-Australian  railway  will  be 
considered,  namely,  Port  Augusta  at  the  head  of  Spencer's  Gulf, 
Ooldea  not  far  from  the  western  border,  and  Tarcoola  about  halfway 
between  the  two.  At  Port  Augusta  the  rainfall  is  about  10  inches  an- 
nually and  at  the  other  stations  it  is  somewhat  less.  Port  Augusta  is 
at  sea-level,  but  Ooldea  and  Tarcoola  each  have  an  altitude  of  about 
500  feet.  In  spite  of  the  low  topography  and  the  small  rainfall  the 
region  is  much  more  varied  and  interesting  than  at  first  might  be  sup- 
posed. At  the  extreme  west  and  extreme  east  are  plains,  and  in  the 
mid-region  low  hills  characterize  the  topography.  Except  for  the 
outcrops  of  pre-Cambrian  rocks,  of  relatively  small  area,  the  region  is  of 
the  Cenozoic  age;  Recent  to  Pleistocene  between  Port  Augusta  and 
Ooldea;  and  Miocene  and  Eocene  west  of  Ooldea.  With  a  single 
exception,  therefore,  this  portion  of  South  Australia  is  geologically 
much  more  recent  than  the  far  north.  In  the  plains  regions  halo- 
phytes  are  the  dominating  plants,  and  in  the  hilly  mid-region  there  is  a 
large  variety  of  species  which  occur  in  larger  numbers  than  might  be 
supposed,  judging  from  the  rainfall  alone.  They  all,  however,  reflect 
the  severity  of  the  environmental  conditions  under  which  they  and 
their  ancestors  have  developed  for  an  immense  period  of  time. 

VEGETATION  AND  THE  ENVIRONMENT  AT  OOLDEA. 
Physiography. 

Ooldea  is  a  station,  really  a  construction  camp  at  the  time  of  my 
visit,  on  the  new  railway  crossing  the  continent,  and  lies  about  one- 
third  of  the  distance  between  Port  Augusta  on  the  east  and  Perth  on 


82  PLANT   HABITS   AND   HABITATS   IN   THE 

the  west.  It  is  427  miles  from  Port  Augusta  and  about  80  miles,  in  a 
direct  line,  from  the  Great  Australian  Bight.  The  main  features  of 
physiographical  interest  are  the  sandhills  to  the  east  and  the  Nullarbor 
Plain  on  the  west.     It  lies  thus  at  the  division  between  the  two. 

The  Nullarbor  Plain  is  a  formation  of  very  great  interest  and  unique- 
ness. Its  east-west  extent  is  about  450  miles  and  its  north-south 
extent  about  200  miles.  The  plain  is  a  sea-floor,  of  the  Mesozoic 
age,  underlain  by  Paleozoic  rocks  (Jutson,  1914:71).  Rocks  of  the 
same  age  outcrop  to  the  west  of  the  plain  in  Western  Australia,  and 
passing  beneath  the  plain  appear  again  about  100  miles  to  the  east 
and  again  at  intervals  farther  toward  Port  Augusta,  as  at  Tarcoola. 
The  Nullarbor  Plain  is  composed  of  limestone  of  a  thickness  approxi- 
mating 500  feet.  The  surface  of  the  plain  is  nearly  level,  as  would 
appear  from  the  fact  that  the  transcontinental  railway  runs  for  330 
miles,  nearly  across  it,  without  a  curve.  The  topography,  however, 
is  not  absolutely  flat,  but  is  very  gently  rolling  and  dips  (less  than 
1  foot  to  the  mile)  to  the  east.  The  limestone  is  covered  by  about  a 
foot  of  red  soil,  although  fragments  of  the  underlying  rock  are  scattered 
about  on  the  surface. 

The  most  striking  feature  of  the  plain,  however,  aside  from  its 
level  character  and  great  extent,  is  the  presence  here  and  there  of 
slight  depressions,  known  as  "dongas,"  which  vary  in  size  from  a  few 
to  hundreds  of  acres.  There  are,  in  addition,  as  would  be  expected  in 
the  limestone  country,  various  fissures  or  openings  of  various  shapes 
and  sizes  which  communicate  with  subterranean  cavities.  Such  open- 
ings are  locally  known  as  "blow  holes"  from  the  air-movements  asso- 
ciated with  them.  The  "blow  holes"  often  appear  to  be  situated  in 
depressions  of  small  extent.  From  the  structure  of  the  plain  it  will 
be  seen  that  such  water  as  falls  on  it  must  quickly  disappear  from  the 
surface.  The  soil  is  so  thin  that  it  constitutes  a  very  inadequate 
water-reservoir.  In  the  dongas,  however,  there  is  a  greater  accumula- 
tion of  soil  and  hence  greater  possibilities  in  the  way  of  water-storage, 
and  in  such  situations  the  vegetation  is  relatively  abundant  and 
wholly  unlike  that  of  the  surrounding  plain. 

The  sandhills  region  east  of  the  Nullarbor  Plain  has  an  east-west 
extent  of  100  miles,  more  or  less,  and  a  larger  extent  in  the  north- 
south  direction.  As  seen  from  Ooldea  and  from  the  railways  trav- 
ersing it,  the  region  has  a  certain  monotony.  The  hills  are  of  nearly 
equal  size  and  run  from  north  to  south,  or  approximately  so.  A 
hardpan  resembling  travertine,  or  desert  limestone,  is  often  present, 
lying  about  1  meter  beneath  the  sandy  surface.  In  the  fairly  deep 
hollows  between  the  ridges,  however,  the  sand  appears  to  be  deeper 
than  on  the  ridges  themselves.  A  short  distance  to  the  north  of 
Ooldea,  where  an  impervious  substratum  underlies  the  hollows,  water 
collects.    This  may  be  either  brackish  or  "sweet."     Such  a  place  is 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  83 

the  well-known  Ooldea  "soak,"  which  has  played  an  important  part 
in  the  activities  of  men  of  all  sorts  who  have  been  in  these  parts. 
Here,  in  a  sandy  depression,  is  to  be  found  a  fairly  good  supply  of 
potable  water  which  appears  to  be  the  only  water  of  its  kind  for  a 
very  great  distance.  Explorers  have  relied  on  it  for  their  supply,  the 
aborgines  come  to  it  frcm  long  distances  in  the  course  of  their  wander- 
ings, and  it  has  been  an  important  factor  in  the  construction  of  the 
railway,  providing  good  water  for  camps. 

The  origin  of  the  sand  on  the  Nullarbor  Plain  and  of  the  sandhills 
appears  not  to  be  surely  known.  So  far  as  the  sand  on  the  plain  in 
the  vicinity  of  the  sandhills  is  concerned  it  may  have  been  moved 
there  by  wind  action  from  the  east,  as  is  popularly  supposed.  Another 
hypothesis  is  to  the  effect  that  the  Nullarbor  Plain  was  laid  down  not 
far  from  shore  and  hence  that  it  had  a  large  admixture  of  coarse 
miaterial,  which  was  set  free  upon  the  elevation  and  the  subsequent 
erosion  of  the  plain.  So  far  as  the  origin  of  the  sand  in  the  sandhill 
region  proper  is  concerned,  Howchin  (1909:67)  suggests  that  it  may 
have  been  derived  from  the  "waste  of  the  granitic  rocks,  which  form 
the  bedrock  of  the  country."  The  same  author  says  also  that  the 
calcareous  material,  which  was  derived  from  "breaking  down  and 
solution  of  Kainozoic  limestone,  has  cemented  the  sand,  in  places, 
into  calcareous  sandrock,  or  has  laid  down  from  solution  a  crust  of 
calcareous  limestone."  Possibly  the  calcareous  core  of  the  sandhills, 
above  noted,  had  some  such  origin. 

The  sandy  soil  in  the  Ooldea  vicinity  is  fairly  coarse  and  permits  the 
rapid  absorption  of  water.  If,  for  example,  a  bucket  of  water  is 
emptied  quickly  on  level  ground  it  spreads  only  slightly  beyond  the 
place  where  it  is  poured  and  sinks  from  sight  almost  immediately. 
This  being  the  case,  it  would  be  expected  that  water  derived  from  the 
rains  would  also  sink  quickly  and  without  appreciable  run-off.  Such  a 
condition  was  observed  at  the  time  of  a  storm  of  September  14.  On 
this  day  there  fell,  between  1  and  4  p.  m.,  0.21  inch  of  rain.  At 
4^  15™  p.  m.  the  soil  was  moist  to  a  depth  of  3.5  cm.  No  rain  occurred 
during  the  night,  but  on  the  following  morning  the  soil  was  found  to  be 
moist  to  a  depth  of  9.5  cm.  Apparently  no  run-off  had  taken  place. 
From  these  observations,  and  from  the  absence  of  all  indications  of 
washing  from  storms,  it  is  concluded  that  such  water  as  falls  on  the 
sandy  soil  at  Ooldea  is  absorbed  at  once,  and  further,  from  the  nature 
of  the  soil  itself,  that  it  is  well  conserved.  These  conditions  must  be 
taken  into  account  when  possible  reasons  for  the  relatively  heavy 
vegetation  of  the  sandhill  region  are  being  sought. 

Climate. 

Ooldea  is  within  the  10-inch  isohyet.  It  is  in  the  region  of  winter 
rains,  but  apparently  more  or  less  precipitation  is  to  be  expected  in 
summer  as  well.    It  will  be  of  great  interest,  in  view  of  the  fairly  abun- 


84 


PLANT   HABITS   AND   HABITATS   IN   THE 


dant  vegetation,  to  establish  not  only  the  amount  of  rainfall  but  its 
distribution  through  the  year.  Very  little  is  accurately  known  as  to 
the  rainfall  at  Ooldea,  for  the  reason  that  permanent  settlement  began 
only  with  the  building  of  the  transcontinental  railway,  which  was 
opened  late  in  the  year  1917.  There  are,  however,  records  for  one 
year  at  a  railway  camp  a  few  miles  to  the  east  and  for  nearly  one  year 
at  Ooldea  itself.  In  addition,  rainfall  reports  are  available  for  Fowler's 
Bay  to  the  south  and  at  Tarcoola  to  the  east,  covering  many  years. 
Nothing  is  known  regarding  the  rainfall  on  the  Nullarbor  Plain  except 
from  inference.  The  precipitation  for  the  years  1917  and  1918  at 
396-mile  Siding  and  at  Ooldea,  supphed  by  the  Bureau  of  Meteorology 
of  the  Commonwealth,  is  given  in  table  14. 

Table  14. — Monthly  rainfall  at  396-mile  Siding  and  at  Ooldea,  South  Australia,  November 
1916  to  September  1918,  inclusive. 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

396-mile  Siding: 
1916           .    ... 

0.19 
1.16 

0.32 
0.73 

1917 

2.5 

1.15 

1.18 

1.24 

0.51 

1.49 

1.48 

0.22 

0.76 

1.69 

Ooldea: 

1917         

1918 

0.0 

0.0 

1.0 

0.6 

0.63 

1.06 

0.16 

1.19 

0.29 

No  record  where is  given. 

Beyond  the  general  facts  that  the  summers  at  Ooldea  are  very  hot 
and  the  winters  are  cool,  little  is  known  of  the  temperature.  Although 
80  miles,  or  more,  intervenes  between  Ooldea  and  the  sea,  it  is  prob- 
able that  here,  as  at  Tarcoola,  where  the  distance  is  even  greater,  the 
southern  winds  are  cool  in  summer  and  cold  in  winter,  and  that  the 
converse  is  true  of  the  winds  from  the  opposite  direction.  Such  winds, 
moreover,  are  undoubtedly  of  very  great  importance  as  factors  modify- 
ing not  alone  the  temperature  but  also  the  relative  humidity  of  the  air, 
and  thus  they  very  directly  affect  the  vegetation.  This  had  already 
been  mentioned  in  the  opening  section  and  need  not  be  further  dwelt 
on  in  this  place. 

Habitats. 

During  my  short  stay  at  Ooldea,  besides  exploring  on  foot  its 
immediate  neighborhood,  I  visited,  through  the  kind  assistance  of 
Mr.  Edwards,  engineer  in  charge  of  construction,  such  localities  as 
were  most  accessible  from  camp  by  motor  car  (railway),  carriage,  or 
saddle-horse.  Thus  the  localities  seen  included  the  eastern  side  of  the 
Nullarbor  Plain,  the  transition  between  the  plain  and  the  sandhills, 
and  the  sandhills  including  the  (1)  Ooldea  Soak,  (2)  the  "oak"  forest  6 
miles  south,  (3)  the  Condensers  and  Station  408,  together  with  the 
region  traversed  between  Ooldea  and  the  last  two,  and  (4)  the  vicinity 
of  Ooldea  itself.    It  will  be  seen  that  there  are  at  least  three  easily 


ARID   PORTIONS  OF   SOUTH   AUSTRALIA.  85 

distinguishable  habitats,  and  probably  more — for  example,  the  hol- 
lows between  the  sandy  ridges  and  the  dongas  on  the  plain.  Study  of 
the  plants  of  these  habitats  would  undoubtedly  show  that  each  has 
a  very  characteristic  vegetation  to  be  associated  with  the  differences 
which  mark  each  habitat. 

Vegetation  of  the  Nullarbor  Plain. 

The  eastern  side  of  the  Nullarbor  Plain,  as  already  mentioned,  has 
a  very  slightly  undulating  surface.  When  one  is  well  out  on  the  plain 
he  can  see  for  many  miles  on  all  sides.  No  topographical  feature 
marks  one  direction  as  opposed  to  another.  At  first  there  is  a  sense 
of  barrenness,  accentuated  by  the  low  relief,  which  is  second  only  to 
that  to  be  felt  in  the  region  about  Oodnadatta;  a  more  careful  exami- 
nation of  the  plain  does  not  fully  justify  this  impression.  A  sparse 
gray-green  plant-covering,  monotonous  in  form  as  well  as  in  color, 
is  to  be  seen  on  every  side.  This  is  composed  of  halophytes  of  various 
species,  among  which  are  chiefly  Atriplex  vesicarium  and  Kochia 
sedifolia.  There  is  also  an  ephemeral  flora  composed  largely  of  grasses 
which  spring  up  after  rains;  but  at  the  time  of  my  visit  (September), 
only  dried  remains  of  such  were  to  be  found.  These  remarks  on  the 
flora  of  the  plain  apply  to  the  plain  proper,  or  rather  to  the  highest 
ground,  which  composes  by  far  the  greatest  percentage  of  its  surface. 

Here  and  there,  in  looking  about,  one  sees  widely  separated  masses 
of  green  of  small  extent,  really  oases,  which  appear  quite  like  small 
islands  in  a  dull-gray  sea.  These  are  the  dongas  with  their  char- 
acteristic vegetation.  Such  dongas  as  were  visited  between  Watson 
and  Ooldea  had  a  few  low  trees  and  shrubs  and  a  fairly  considerable 
dead,  herbaceous  flora;  but  the  plants,  the  woody  forms  especially, 
appeared  to  consist  of  but  a  small  number  of  species,  although  so  few 
dongas  were  seen  that  no  dogmatic  statement  in  this  regard  would  be 
warranted.  Certain  of  these  depressions  near  the  Fowler's  Bay  road 
had  Acacia  tetragonophylla,  A.  aneura,  and  a  "weeping  sandal-wood," 
possibly  Pittosporum  phillyrceoides.  The  kind  as  well  as  the  abundance 
of  plants  in  the  dongas  illustrate  in  a  very  striking  manner  the  very 
great  importance  of  the  topography  and  of  the  substratum  as  factors 
in  the  vegetation  of  an  arid  region.  A  similar  condition  is  to  be  found 
in  southern  Algeria  (Cannon,  1913:31).  There,  for  example,  are 
depressions  (dayas)  which  are  the  centers  of  small  drainage  systems 
in  which  there  is  an  accumulation  of  soil  and  which  have  subterranean 
drainage,  so  that  an  excess  of  salts  in  the  soil  solution  appears  not  to 
occur.  Owing  in  part  to  drainage  into  the  basins  after  storms,  and  in 
part  to  the  great  amount  of  soil  in  them,  constituting  important 
reservoirs,  the  dyas  and  dongas  alike  have  relatively  good  water 
relations  and  their  fairly  abundant  flora  follows  as  a  matter  of  course. 


86  PLANT   HABITS   AND   HABITATS   IN   THE 

Vegetation  about  Ooldea. 

At  and  about  Ooldea,  and  in  fact  on  all  of  the  sandhills  of  this  region, 
so  far  as  my  observation  extended,  there  is  a  surprising  wealth  of 
woody  vegetation.  Views  across  country  reveal  an  undulating  surface 
well  covered  with  low,  spreading  trees  and  shrubs.  The  trees  are  so 
numerous  that  often  the  branches  intermingle,  completely  hiding 
the  ground  beneath.  In  the  immediate  vicinity  of  Ooldea  the  leading 
trees  and  shrubs  are  species  of  Acacia,  among  which  the  following  were 
seen:  Acacia  aneura,  A.  hrachystachya,  A.  colletioides,  A.  kempeana,  A. 
linophylla,  A .  oswaldii,  A .  randelliana,  A .  salicina,  and  A .  tetragonophylla. 

The  following  notes  on  the  local  distribution,  especially  of  these 
species,  were  made:  Acacia  aneura,  the  "mulga,"  forms  a  small,  fairly 
dense  tree  (plate  19a)  and  occurs  in  two  very  distinct  forms,  that  with 
narrow  and  that  with  broad  phyllodia  (plate  20,  b  and  c) .  It  is  fairly 
abundant  at  Ooldea.  Acacia  hrachystachya  is  also  common  about 
Ooldea,  forming  a  large  and  attractive  shrub.  The  phyllodia  are 
linear,  long,  and,  like  most  of  the  foliage  of  the  sandhill  community,  of 
a  gray-green  color.  Acacia  colletioides  is  common  about  6  miles  to  the 
south.  It  is  a  rather  diffuse  shrub  and  bears  short  spinescent  phyllo- 
dia (plate  20a).  Acacia  kempeana,  a  shrub  of  compact  habit  of 
growth,  has  a  relatively  heavy  covering  of  fairly  large  phyllodia  and 
is  common  at  Ooldea.  Acacia  linophylla,  also  common  about  Ooldea, 
forms  a  small  tree,  possibly  3  to  5  meters  in  height.  In  foliage-habit  it 
is  quite  the  same  as  the  same  species  previously  seen  at  Oodnadatta. 
Acacia  oswaldii,  a  small  tree,  was  seen  about  6  miles  south  of  Ooldea. 
Acacia  randelliana  is  a  shrub,  3  or  more  meters  high,  and  common 
about  Ooldea.  Acacia  salicinia,  a  small  tree  with  rather  prominent 
phyllodia,  is  frequently  seen  in  the  neighborhood.  Acacia  tetragono- 
phylla, which  forms  a  small  tree,  was  seen  only  on  the  edge  of  the  plain 
and  appears  not  to  occur  commonly  in  the  sandhills. 

With  the  exceptions  noted,  the  acacias  appear  to  be  very  generally 
distributed  on  the  sandhills  about  Ooldea,  but  how  far  they  are  con- 
fined to  the  ridges  was  not  noted.  Among  other  woody  species  seen 
in  the  same  habitat  were  the  "bullock  bush,"  Heterodendrum  olecefolium, 
a  small  tree  well  covered  with  small  leaves.  Dodoncea  attenuata  and 
Olceria  muelleri  also  were  fairly  common  on  the  sandhills. 

Among  other  species  of  interest  was  the  "oak,"  Casuarina  lepido- 
phloia,  in  some  respects  the  most  important  species  of  the  region. 
It  occurs  in  the  hollows  between  the  ridges  to  the  south  of  Ooldea  as 
well  as  on  the  ridges  themselves.  The  "oak"  makes  open  forests  and 
is  said  to  extend  as  such  to  the  bight  on  the  south.  It  is  of  great  im- 
portance at  present,  as  the  wood  is  largely  used  as  fuel  in  distilling 
water  at  the  "condensers,"  for  uses  of  the  railway  in  the  region.  The 
demand  is  so  heavy  for  wood  that  fairly  young  trees  are  cut,  with 
serious  portent  to  the  species  in  this  portion  of  the  state. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  87 

With  other  woody  species,  fairly  common,  may  be  included  Euca- 
lyptus incrassata  var.  dumosa.  This  has  the  mallee  habit  of  growth 
and  is  also  utilized  as  fuel  along  with  the  "oak."  In  distribution  this 
species  frequently,  if  not  usually,  occurs  to  the  exclusion  of  other  woody 
forms,  but  a  spinifex,  Triodia  irritans,  is  often  associated  with  it.  In 
case,  however,  other  woody  species  occur  with  the  mallee,  the  grass 
seems  to  be  wanting.  As  to  the  habit  of  the  mallee,  it  has  open, 
canopy-like  shoots,  of  many  stems,  and  thus  is  easily  recognizable 
from  a  distance.  In  addition  to  this,  the  most  abundant  of  the  genua 
about  Ooldea,  there  are  two  others  of  the  genus.  Of  these.  Eucalyptus 
pyriformis  occurs  very  sparingly  between  Ooldea  and  Ooldea  Soak, 
3  miles  to  the  north  (plate  21a).  The  species  is  of  characteristic 
mallee  form,  and  bears  large  flowers  and  fruits  (plate  22a).  Accord- 
ing to  Maiden,  it  is  one  of  the  handsomest  species  of  the  genus,  "be- 
cause of  the  large  size  and  showiness  of  the  flowers  and  the  large  size 
and  ornamental  character  or  at  least  grotesqueness  of  the  fruits." 
The  fruits  are  about  5  cm.  in  diameter  and,  occurring  in  groups,  they 
give  a  striking  appearance  to  the  open  shoot.  The  third  species  of 
Eucalyptus  seen  among  the  sandhills  was  a  dwarf  form,  E.  leucoxylon 
var.  macrocarpa  (plates  21b  and  22c).  This  was  seen  at  Station  408, 
where  it  forms  a  small  thicket.  It  is  from  1  to  2  meters  high,  appar- 
ently somewhat  smaller  than  is  usual  for  the  variety. 

Several  woody  species  were  seen  only  here  and  there  and  appeared 
not  to  be  very  common,  or  at  least  not  to  be  of  very  general  distribution 
in  the  region.  Among  these  may  be  included  Eremophila  alternifolia, 
which  is  fairly  abundant  near  Ooldea  and  also  occurs  on  flats  between 
the  sandy  ridges  (Black,  1917).  The  same  author  also  says  that 
Eremophila  paisleyi  and  Pholidia  scoparia  are  to  be  found  about 
Ooldea.  All  of  these  species  of  Eremophila  were  seen  at  Copley, 
where  E.  alternifolia  is  confined  to  the  banks  of  washes  or  to  other 
situations  where  the  water  conditions  are  relatively  good.  Fusanus 
acuminatus,  the  "native  peach,"  is  not  uncommon  in  the  sandhills 
near  the  camp.  Many  other  species  occur  scatteringly,  several  of 
considerable  interest.  Of  these,  Leptospermum  Icevigatum  var.  minus 
was  seen  at  Ooldea  Soak  only  (plate  22b). 

As  has  been  mentioned  already,  Ooldea  Soak  is  a  hollow  among  the 
sandhills  about  3  miles  to  the  north  of  the  camp.  There  is  more  than 
one  depression  at  the  place,  but  all  appear  much  alike.  The  higher 
ground  carries  a  very  good  population  of  small  trees,  acacias  and  mallee, 
but  in  the  depressions  there  is  very  little  growth.  It  is  here  that  in 
certain  hollows,  but  not  in  all,  the  Leptospermum  is  to  be  found.  The 
species  is  confined  to  such  depressions  as  have  potable  water  and 
avoids  such  as  have  water  that  is  brackish.  It  is  an  interesting  fact 
that,  although  the  water-table  of  the  portion  of  the  soak  where  the 
Leptospermum  grows  is  little  if  any  over  1  meter  deep,  and  the  water 


88  PLANT   HABITS   AND    HABITATS   IN   THE 

itself  is  perfectly  suited  to  the  needs  of  the  sandhills  species  growing 
round  about,  yet  they  appear  never  to  have  encroached  on  the  soak 
more  than  they  do  at  present.. 

Of  other  isolated  species,  one  of  the  most  curious  is  the  flat-stemmed 
and  leafless  Bossicea  walker  (plate  29a)  .  This  low  shrub  forms  a  small, 
thicket-like  growth.  It  was  seen  in  several  fairly  widely  separated 
places,  among  which  was  a  sandy  ridge  immediately  north  of  Sta- 
tion 408.  At  this  place,  and  not  far  from  the  Bassioea,  there  occur  a 
few  specimens  of  a  yet  more  curious  shrub,  Hakea  multilineata.  This 
is  a  tall  shrub  with  very  long  coriaceous  and  strap-like  leaves  of  up- 
right habit  (plate  29,  b  and  c).  The  large  and  stiff  spikes  of  flowers, 
"bottle  brushes,"  add  to  the  wierdness  of  the  plant.  In  the  same 
neighborhood  as  the  two  foregoing  were  Acacia  salicina,  CaUiiris 
verrucosa,  Eucalyptus  leucoxylon  var.  macrocarpa,  Melaleuca  uncinata 
(plate  29d),  and  Gravillea  stenobotrya.  Of  these,  CalUtris,  the  "pine," 
is  a  small  tree  at  the  only  place.  Station  408,  where  it  was  seen. 

Gravillea  stenobotrya,  one  of  the  "beef  woods,"  is  a  species  of  con- 
siderable interest  (plates  24a  and  25c) .  It  becomes  a  fairly  large  shrub, 
3  meters  or  more  in  height,  and  has  a  very  open  habit  of  growth. 
The  leaves  are  long  and  narrow  and  do  not  appear  to  be  very  abundant. 
It  is  thus  apparent  that  the  transpiring  surface  is  relatively  small. 
The  specimens  of  the  beef  wood  especially  examined  were  situated 
on  the  summit  of  a  sandy  ridge  at  the  condensers.  A  point  of  special 
interest  in  association  with  the  species  is  its  habit  of  storing  water 
in  the  roots.  It  appears  that  it  is  one  of  possibly  two  woody  species 
of  the  region  (the  other  is  the  so-called  "water  mallee")  which  does 
this.  Mr.  Jay,  of  the  condensers,  very  kindly  demonstrated  the  roots 
for  me.  After  removing  the  surface  soil  to  a  depth  of  approximately 
60  cm.,  several  horizontal  roots,  3  to  4  cm.  in  diameter,  were  laid  bare. 
These  were  cut  into  lengths  of  about  30  cm.  and  set  on  end  in  a  bucket. 
After  a  few  minutes  moisture  accumulated  at  the  lower  ends,  but  owing 
to  its  being  at  the  close  of  a  period  of  drought  not  enough  water  was 
present  to  run  into  the  receptacle.  The  short  lengths  of  root  were 
relatively  heavy.  When  the  bark  was  stripped  off,  much  moisture 
was  found  in  the  region  of  the  cambium.  I  was  informed  that  at  less 
dry  seasons  of  the  year  and  in  more  favorable  situations  at  all  times, 
the  manipulation  of  the  roots  in  the  manner  above  described  would 
surely  result  in  sufficient  water  for  drinking. 

In  addition  to  the  water  mallee  and  the  beef  wood  (perennials),  there 
is  the  annual  "parakeelya,"  Calandrinia  balonensis,  which  also  has 
the  capacity  of  storing  water.  At  the  time  of  my  visit  this  little  species 
was  in  flower.  It  is  a  low  form  with  numerous  very  fleshy  and  rigid 
leaves.  The  plants  are  much  sought  after  by  animals  which  depend  on 
them  to  a  certain  extent  for  their  drinking  water.  They  have  the  ability 
of  retaining  their  turgescence  for  a  considerable  time  after  removal  from 
the  soil,  and  even  if  placed  in  the  warm  sunshine  they  wilt  only  slowly. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  89 

Transition  from  the  Sandhills  to  the  Nullarbor  Plain. 

Along  the  eastern  edge  of  the  great  plain  there  is  at  Ooldea  a  scat- 
tered vegetation  in  which  elements  from  the  two  physiographic  areas 
mingle  to  a  certain  extent.  The  soil  conditions  appear  to  differ  from 
those  of  the  plain  in  the  greater  depth  of  soil  brought  about  probably 
by  drifting  of  the  sand  from  the  adjacent  sandhills.  Because  of  this 
condition  the  water  relations  of  the  transition  are  somewhat  better 
than  they  are  for  the  plain  as  a  whole.  Here  occur,  among  other 
species,  Kochia  sedifolia,  which  possibly  is  most  numerous;  EremopMla 
alternifolia  and  possibly  other  species  of  EremopMla,  Acacia  kempeana, 
A .  aneura,  and  A .  tetragonophylla.  A  few  specimens  of  Casuarina  lepido- 
phloia  were  seen  along  the  road  to  Fowler's  Bay  and  Cassia  sp.  in 
fairly  large  numbers.  In  places  rather  large  areas  were  covered  with 
dead  shrubs  which  had  not  been  able  to  withstand  the  drought  of  some 
preceding  year;  these  appeared  to  be  cassias.  Finally,  there  were 
remains  of  grasses,  species  not  determined,  and  among  other  herba- 
ceous forms,  here  and  there  appeared  the  cheerful  flowers  of  Calan- 
drinia  balonensis  with  its  odd  fleshy  and  bright-green  leaves. 

Leaf-Form  and  Leaf-Size. 

All  of  the  perennials  of  the  Ooldea  region  have  pronounced  xerophy- 
tic  characters,  as  would  be  expected  from  the  nature  of  the  environ- 
ment to  which  the  vegetation  is  exposed.  Without  taking  up  this 
feature  further  at  this  time,  attention  may  be  called  to  the  relatively 
narrow  leaves,  or  phyllodia,  of  the  species.  Indeed,  it  may  be  said 
that  all  species  which  are  not  aphyllous  bear  leaves  of  this  character. 
The  length  of  the  leaves,  or  phyllodia,  averages  approximately  20 
times  the  width. 

VEGETATION  AND  ENVIRONMENT  AT  TARCOOLA. 

Physiography. 

Tarcoola  is  the  center  of  a  gold-field  of  secondary  importance  and 
is  connected  with  Wilgena  Run,  a  "station"  of  about  3,000  square 
miles,  formerly  owned  by  A.  J.  Cocks  esq.,  of  Adelaide,  whose  knowl- 
edge of  the  region  has  been  generously  placed  at  my  disposal  and  who 
in  various  ways  very  kindly  forwarded  my  studies  of  the  region  im- 
mediately around  the  village. 

Tarcoola  is  257  miles  west  of  Port  Augusta  and  lies  392  feet  above 
the  sea.  Like  Ooldea,  it  lies  on  the  south  edge  of  the  western  plateau. 
The  village  is  about  100  miles,  as  the  crow  flies,  from  the  Bight. 
Between  it  and  Ooldea  the  country  is  undulating  and  about  Tarcoola 
it  is  hilly.  To  the  east  the  general  level  sinks  and  the  flat  salt-lakes 
region  begins.  At  Tarcoola  itself  the  plains  between  the  hills  con- 
stitute the  largest  percentage  of  the  surface.  The  Tarcoola  hills,  in 
part  at  least,  are  granitic,  of  pre-Cambrian  age,  related  to  the  out- 


90  PLANT   HABITS   AND   HABITATS   IN   THE 

cropping  rocks  at  Wynbring,  west  of  Tarcoola,  and  to  the  ancient 
rocks  to  the  west  of  Nullarbor  Plain  in  Western  Austraha. 

The  soil  in  the  immediate  neighborhood  of  Tarcoola  is  various. 
On  the  hills  it  appears  to  be  very  coarse  and  on  the  adjacent  plains 
there  is  a  large  admixture  of  sand  brought  from  the  higher  ground. 
In  places  there  is  to  be  found  clay,  or  at  least  soil  of  a  very  fine  char- 
acter resembling  clay,  and  also  a  white  subsoil,  apparently  travertine 
or  desert  limestone.  Some  sandy  stretches  to  the  north  of  the  village 
are  of  very  considerable  extent;  and,  finally,  there  are  depressed 
areas,  of  various  sorts,  in  which  the  soil  carries  a  large  amount  of  salts. 

With  the  differences  in  soil  and  in  topography  are  associated  differ- 
ences in  the  water  relations  as  well,  and  without  doubt  a  close  study 
of  the  vegetation  of  the  region  would  reveal  a  variation  in  its  flora 
intimately  connected  with  such  differences  in  the  subterranean  en- 
vironment. 

Rainfall  and  Temperature. 

The  rainfall  at  Tarcoola  averages  7.71  inches  over  a  period  covering 
9  years,  but  the  variation  from  year  to  year  is  considerable.  Thus 
the  highest  recorded  (1910)  was  12.35  and  the  lowest  (1905)  was  2.82 
inches.  The  record  for  Tarcoola  in  1912  was  6.43  inches.  There 
were  33  wet  days  during  the  year.  The  wettest  month  was  July, 
during  which  1.8  inches  of  rain  fell.  On  March  9  of  the  same  year  1.12 
inches  of  rain  occurred.  The  type  of  rainfall,  therefore,  conforms  to 
that  of  the  other  arid  stations  visited.  In  1912  at  Port  Augusta 
10.92  inches  of  rain  fell  during  66  days.  It  will  be  seen,  therefore, 
that  an  average  of  0,19  inch  occurred  each  rainy  day  at  Tarcoola  and 
only  0.16  inch  at  Port  Augusta.  It  is  of  interest  to  note  that  at  Oodna- 
datta  the  average  daily  amount  during  rainy  days  was  0.15  inch  and 
at  Copley  (Farina)  0.24  inch.  Inasmuch  as  the  penetration  of  the 
rains  is,  other  conditions  being  equal,  directly  connected  with  the 
amount  of  the  rain,  it  would  appear,  so  far  as  the  year  1912  is  con- 
cerned, that  the  rain  penetration  at  Tarcoola  was  probably  fairly, 
at  least  relatively,  good.  About  65  per  cent  of  the  rainfall  at  Tarcoola 
occurs  during  the  cool  season,  April  to  October,  while  the  percentage 
at  Port  Augusta  is  for  this  season  somewhat  greater,  being  approxi- 
mately 75  per  cent. 

The  summers  at  Tarcoola  are  hot  and  the  winters  cool,  as  would  be 
expected  from  the  situation  of  the  place.  Mr.  Harry  Deadman,  of 
Tarcoola,  who  is  well  acquainted  with  its  climate,  informs  me  that  the 
summer  maximum  sliade  temperature  is  about  118°  F.  The  tempera- 
ture is  greatly  influenced  by  the  desert-arid  region  to  the  north  and 
by  the  Bight  to  the  south,  though  the  latter  is  about  100  miles  distant. 
Summer  winds  from  the  north  are  extremely  hot  as  well  as  dry,  while 
those  from  the  south,  in  summer,  quickly  cause  a  lowering  of  the  tem- 
perature. 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  91 

Vegetation. 

Views  from  the  low  hills  at  Tarcoola  reveal  a  fairly  abundant  as 
well  as  fairly  varied  vegetation.  As  far  as  the  eye  can  reach  shrubs 
and  small  trees  give  the  prevailing  tone,  gray-green,  to  the  landscape, 
with  here  and  there  darker  patches  of  green  or  lighter  masses  of  gray. 
There  are  saltbushes  in  plenty  on  the  flats  and  scrub  elsewhere.  One 
can  identify  the  dark-green  "sandal-wood,"  the  "tea-trees,"  the  "oaks," 
as  well  as  the  "mulga"  and  "myall."  That  there  is  considerable  vege- 
tation in  the  region  is  further  suggested  by  the  fact,  as  mentioned 
above,  that  it  constitutes  a  portion  of  the  Wilgena  Run,  which  at  one 
time  supported  30,000  sheep,  in  addition  to  numerous  cattle  and  camels. 

The  habitats  examined  during  my  short  stay  at  Tarcoola  comprised 
ths  low,  fiat,  granitic  hills  close  to  town,  the  slopes  of  these  hills,  and 
the  lowlands  about  them  and  to  the  north.  In  this  reconnaissance 
only  the  most  conspicuous  features  of  the  vegetation  were  taken  into 
account. 

The  hills  appear  to  be  the  most  arid  of  all  the  habitats.  This  is 
owing  to  the  coarse  character  of  the  soil.  We  find,  accordingly,  that 
the  ve  etation  of  the  hills  is  relatively  sparse  and  also  that  it  is  of  a 
characteristic  markedly  xerophytic  kind.  The  slopes  of  the  hills 
carry  the  largest  number  of  species  as  well  as  the  greatest  number  of 
individuals.  Of  the  hills'  vegetation,  the  following  species  constitute 
a  prominent  part:  Acacia  aneura,  A.  rigens,  A.  tarcuHensis,  A.  tetragon- 
ophylla,  Cassia  sturtii,  Casuarina  lepidophloia,  Eremophila  latrohei,  E. 
rotundifoUa,  E.  paisleyi,  Trichinium  incanum,  and  others. 

Acacia  aneura,  the  "mulga,"  is  sparingly  abundant  on  the  southern 
slopes  of  the  granite  hill,  which  for  convenience  will  here  be  referred 
to  as  Gold  Hill,  from  the  mining  operations  carried  on,  near  and  south- 
west of  Tarcoola  village.  It  occurs  to  a  certain  extent  also  on  other 
portions  of  the  hill.  In  and  by  the  side  of  a  shallow  wash  on  the 
southern  side  of  Gold  Hill,  in  addition  to  A.  aneura,  are  to  be  found 
A.  tetragonophylla,  A.  tarculiensis,  and  Trichinium  incanum.  The 
last  named,  a  low,  rounded  shrub,  occurs  only  sparingly  on  the  southern 
slope  of  the  hill. 

On  the  eastern  side  of  Gold  Hill  is  a  fau-ly  dense  population  of  shrubs, 
mainly  halophytes,  of  which  Kochia  decaptera  appears  to  be  the  most 
numerous.  Here  also  occur  Casuarina  lepidophloia  and  Eremophila 
rotundifoUa,  as  well  as  scattering  specimens  of  E.  latrohei  and  Acacia 
tarculiensis.  Eremophila  rotundifoUa  is  a  very  striking  shrub.  The 
shoot  is  of  open  habit  of  growth.  The  leaves  are  small,  saddle-shaped, 
and  leathery  in  texture  (plate  24b).  No  species  of  the  genus,  seen 
at  Tarcoola  or  elsewhere,  is  a  more  evident  xerophyte  than  this  one. 

The  lower  slopes  of  Gold  Hill,  where  the  soil  is  relatively  moist 
because  of  seepage,  have  a  fairly  abundant  perennial  flora,  much  of 


92  PLANT   HABITS   AND   HABITATS   IN   THE 

which  is  halophytic.  Thus,  on  the  upper  portion  of  such  slopes  Kochia 
sp.  is  dominant,  while  below  are  various  species  of  Atriplex  and  Bassia. 
Along  the  washes  one  finds  Lycium  australe  and  Pimelea  microcephala, 
as  well  as  a  few  specimens  of  Acacia  rigens  (plates  25a  and  24c). 

On  the  higher  flats,  upon  which  the  village  is  situated,  the  most 
conspicuous  shrub  is  Acacia  tarculiensis  (plate  24d).  As  the  name 
indicates,  Tarcoola  is  the  type  habitat  of  the  species.  This  shrub  is 
2  meters  or  less  in  height,  with  a  shapely  shoot,  well  clothed  with 
phyllodia,  which  are  of  fair  size  and  placed  in  a  vertical,  upright 
position  on  the  branchlets.  The  young  phyllodia,  at  least,  are  covered 
with  a  somewhat  sticky  substance,  possibly  resinous,  which  may  be 
of  importance  as  protection  against  destructive  water-loss.  In  the 
same  neighborhood  and  at  the  time  of  my  visit  to  Tarcoola  in  Septem- 
ber, there  were  several  species  of  annuals,  but  no  study  of  these  was 
made.  There  was  seen  a  very  striking  community  of  ''everlastings," 
which  made  a  dense  carpet-like  growth,  many  meters  in  extent,  to 
the  total  exclusion  of  other  species  of  annuals. 

Not  far  to  the  north  of  Gold  Hill,  a  second  hill,  also  granitic,  was 
visited.  On  the  south  the  slope  of  this  hill  is  fairly  abrupt,  but  on  the 
opposite  face  it  is  gradual  and  merges  insensibly  with  a  wide-spreading 
sandy  plain  which  hes  to  the  north  of  the  village.  The  vegetation  of 
the  hill  appears  to  be  about  the  same  as  that  of  Gold  Hill,  but  a  view 
over  the  plain  from  the  hill  shows  that  the  general  character  of  its 
woody  vegetation  is  rather  different  from  that  of  the  lowlands  near 
Gold  Hill,  for  example.  Thus  there  are  trees  in  some  abundance, 
although  not  large  in  size,  and  numerous  shrubs.  The  plain  very 
evidently  carries  the  largest  perennial  population  of  any  habitat  at 
Tarcoola.  At  the  north  base  of  the  hill  in  question  Acacia  tarculiensis 
is  to  be  found;  below  and  beyond  A.  aneura  can  be  easily  recognized, 
and  still  further,  at  the  border  between  plain  and  hill,  is  a  belt  of 
Myoporum  platycarpum;  finally  there  may  be  seen,  scatteringly  over 
the  plain,  Casuarina  lepidophloia.  Masses  of  yellow  blazed  here  and 
there,  where  groups  of  Cassia  eremophila  were  in  flower.  Between 
the  larger  shrubs  and  trees  the  blue-green  foliage  of  Kochia  decaptera 
occupied  the  interstices,  like  the  background  of  an  oriental  rug. 

When  examined  more  closely,  the  plain  to  the  north  of  Tarcoola, 
or  at  least  its  southern  portion,  is  composed  of  fairly  coarse,  sandy 
soil,  apparently  derived,  at  least  in  part,  from  the  disintegration  of 
the  hill  already  mentioned  as  lying  on  its  south.  There  was  little  or 
no  evidence  of  washing  from  the  rains.  It  is  likely,  therefore,  that 
the  rainfall  mostly  penetrates  where  it  falls,  so  that  the  maximum 
benefit  to  the  plants  is  had.  That  this  is  the  case  is  also  suggested 
by  the  relatively  large  number  of  large  woody  plants,  especially  of 
trees,  which  have  survived  the  destructive  influences  of  man  and  of 
animals.    The  growth-habits  of  the  species  of  the  plain  have  in  the 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  93 

main  been  sufficiently  characterized  in  different  parts  of  this  study. 
It  will  be  sufficient,  therefore,  to  sketch  briefly  the  habits  of  one  not 
hitherto  met,  namely,  Cassia  eremophila.  This  attractive  shrub  was 
in  flower  at  the  time  of  my  visit.  An  especially  interesting  feature 
is  the  character  of  its  leaves.  It  is  one  of  the  few  species  outside  of 
the  acacias  which  has  phyllodia.  The  leaf  is  compound,  with  leaflets 
about  10  mm.  in  length.  The  leaf-stalk  is  broad,  however,  and  upon 
the  falling  of  the  leaflets  it  persists  in  carrying  on  the  photosynthetic 
function.  This  is  exactly  the  occurrence  in  certain  species  of  Acacia, 
although  in  some  the  leaf-forming  habit  has  been  lost  and  phyllodia 
only  are  organized. 

VEGETATION  AND  ENVIRONMENT  AT  PORT  AUGUSTA. 
Physiography. 

Port  Augusta  is  situated  at  the  northern  termination  of  Spencer's 
Gulf.  The  topography  of  the  region  immediately  about  the  place 
is  very  diverse.  Some  of  the  most  striking  physiographical  features 
may  be  briefly  described.  The  head  of  the  gulf,  here  very  narrow, 
is  surrounded  by  a  belt  of  sandhills,  usually  of  no  great  height.  Back 
of  the  dunes,  more  especially  to  the  north,  are  depressions  which  do 
not  have  adequate  surface  drainage,  or  none  at  all,  and  which  carry 
an  excess  of  salts.  These  are  the  outlyers  of  the  extensive  ''lake" 
district,  containing  Lake  Gairdner,  Lake  Torrens,  and  (among  others) 
Lake  Lagoon,  the  latter  extending  about  200  miles  north  and  west, 
and  somewhat  less  to  the  north.  To  the  west  and  southwest  and 
beginning  about  15  miles  distant  are  flat-topped  (pre-Cambrian) 
"tent-hills,"  remnants  of  a  formerly  extensive  higher  land-level. 

The  country  immediately  surrounding  the  table  mountains  is  some- 
what higher  than  the  belt  of  dunes  and  salt  spots  nearer  the  gulf. 
Turning  to  the  east  we  find,  beyond  the  lowlands,  western  members  of 
the  Flinders  Ranges  extending  in  a  generally  north-south  direction  and 
distant  about  12  miles  from  the  gulf.  Between  the  foothills  and  the 
dune-salt-spot  region  by  the  gulf  are  gently  sloping  plains  or  bajadas. 
The  mountains  are  sierras  with  sharply  irregular  sky-Une,  character- 
istic of  the  mountains  of  arid  regions.  Of  the  highest  peaks,  the 
most  important  are  Mount  Brown  (altitude  3,500  feet)  and  Devil's 
Peak,  about  as  high.  It  will  be  seen,  therefore,  that  the  situation  of 
Port  Augusta,  in  relation  to  the  mountains  and  to  the  gulf,  as  well 
as  to  the  vast  arid  region  to  the  north  and  west,  is  such  as  to  give  the 
region  climatic  conditions,  on  the  whole,  unlike  those  of  any  of  the 
regions  elsewhere  met  in  the  course  of  the  present  studies.  There  is 
also  not  a  little  variation  in  plant  conditions  because  of  the  differences 
in  altitude  and  those  of  aspect,  soil,  drainage,  and  moisture  which 
altitude  differences  entail. 


94  PLANT   HABITS   AND   HABITATS   IN   THE 

Rainfall. 

Port  Augusta  lies  just  within  the  10-inch  isohyet,  having  a  rainfall 
of  9.43  inches,  the  average  for  52  years.  The  greatest  rainfall  here 
recorded  for  one  year,  up  to  and  including  1912,  was  17.52  inches, 
and  the  least  was  2.21  inches,  the  ratio  thus  being  nearly  8  to  1.  It  is 
of  interest  to  note  that  the  ratio  is  about  the  same  as  at  Copley,  but 
very  much  greater  than  at  Tarcoola,  although  the  average  annual 
rainfall  at  all  of  these  places  does  not  vary  greatly.  The  largest  pro- 
portion of  the  rain  falling  at  Port  Augusta,  which  amounts  to  about  75 
per  cent  of  the  whole,  occurs  in  the  cool  season.  This  is  approximately 
10  per  cent  less  than  the  rainfall  for  the  corresponding  period  at  Tar- 
coola and  15  per  cent  more  than  Copley.  The  distribution  throughout 
the  year  is  such  as  to  accentuate  the  arid  conditions  for  the  region, 
and  since  rainfall  expectancy,  the  season  of  its  occurrence,  and  the 
actual  amount  are  important  factors  in  the  aridity  of  a  region,  it  is 
seen  that  Port  Augusta  must  be  considered  fairly  arid. 

Temperature. 

The  climate  of  Port  Augusta  is  characterized  by  cool  winters  and 
hot  summers.  The  latter,  as  shown  above,  are  also  dry.  The  mean 
annual  temperature  is  66.2°  F.,  about  1°  less  than  that  of  Copley 
and  2°  less  than  the  mean  at  Oodnadatta.  The  absolute  maximum 
(28  years'  records)  is  117°  and  the  absolute  minimum  is  31.4°.  The 
mean  number  of  days  in  the  year  having  a  temperature  above  90°  is 
67.4,  and  the  mean  number  of  nights  with  a  temperature  under  40° 
is  16.6.  The  monthly  course  of  the  temperature  at  Port  Augusta  is 
given  in  table  7. 

Vegetation. 

The  vegetation  at  and  in  the  neighborhood  of  Port  Augusta,  as 
would  be  expected  from  the  nature  of  the  physiography  of  the  place, 
is  very  diverse,  and  in  earlier,  pre-colonial  times,  must  have  been 
fairly  abundant.  This  is  indicated  not  only  by  the  natural  flora,  but 
by  such  introduced  plants  as  have  escaped  and  live  under  natural  con- 
ditions, or  by  such  cultivated  species  as  grow  without  irrigation. 
Among  the  latter  may  be  mentioned  Schinus  molle,  which  occurs  in  all 
parts  of  the  town.  The  species  forms  an  extensive  superficial  root- 
system  which  radiates  far  from  the  main  stem.  Opuntia  monocantha 
also  is  fairly  common  and  Tamarix  crus-gallica  occurs  about  the  village. 
Possibly  the  most  striking  introduced  plants  which  reproduce  them- 
selves naturally  in  the  Port  Augusta  region  are  species  of  Mesem- 
bryanthemum,  as  M.  crystalUnum,  which  grow  on  the  sandhills  near  the 
coast. 

In  and  close  to  town  several  species  of  shrubs  and  trees,  native  to 
the  region,  are  of  interest.  In  the  parks,  for  example,  one  finds 
Acacia  rigens  and  A.  salicina,  and  among  other  species,  Nitraria 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  95 

schceberi.  Among  the  most  striking  of  the  woody  perennials  to  be  seen 
is  Avicennia  officinalis,  which  occurs  between  tides  along  the  gulf. 
Avicennia,  the  mangrove,  forms  fairly  dense  pigmy  forests  of  narrow 
width.  At  high  tides  the  trees  are  entirely  covered  with  water,  and  at 
low  tides  they  are  left  high  and  dry  on  the  sandy  beach.  Radiating 
from  each  tree  are  lines  of  short  shoots  which  spring  from  superficial 
roots.  These  shoots,  usually  10  to  15  cm.  in  length,  appear  to  develop 
into  the  mature  form  under  appropriate  conditions,  although  all  have 
the  appearance  of  being  merely  pneumatophores.  In  the  zone  where 
they  occur  the  mangroves  are  the  sole  species  of  flowering  plants; 
but  farther  from  the  water,  although  apparently  not  wholly  above  the 
reach  of  the  highest  tides,  is  a  belt  of  Salicornia  sp. 

In  earlier  times  the  low  hills,  most  of  which  are  dunes  and  lie  close 
to  the  waters  of  the  gulf  at  Port  Augusta,  must  have  had  a  fairly 
dense  population  of  trees  and  shrubs,  if  one  can  judge  from  the  woody 
plants  found  in  occasional  undisturbed  places.  Among  other  species, 
the  most  striking  forms  are  Acacia  rigens  and  A.  salicina,  as  before 
noted,  as  well  as  Casuarina  lepidophloia.  The  shrubs  include  Nitraria 
schceberi,  Sccevola  collaris,  Cassia  sp.,  and  some  halophytes,  especially 
species  of  Kochia. 

Large  areas  occur  where  there  is  an  excess  of  salts  in  the  soil.  Here 
were  found  species  of  Atriplex,  Bassia,  Kochia,  Nitraria,  and  Salicornia, 
among  others. 

Upon  leaving  the  dunes  and  salt  spots  near  the  coast,  there  is  a 
marked  change  in  the  character  of  the  vegetation.  In  the  neighbor- 
hood of  Sterling,  for  example,  numerous  specimens  of  Eucalyptus  sp. 
are  scattered  about  the  plain,  and  along  the  wash  leading  away  from 
the  mountains  is  E.  rostrata.  With  the  increase  in  altitude  as  the 
foothills  are  crossed  the  number  of  individuals  becomes  greater  and 
the  character  of  the  vegetation  indicates  a  larger  rainfall.  On  either 
side  of  the  highway  leading  to  Saltia,  where  the  foothills  spring  fairly 
abruptly  from  the  plain,  there  is  to  be  found  a  thick  covering  of 
Atriplex  and  Kochia,  and  along  the  lower  slopes,  near  where  washes 
break  through,  are  small  thickets  of  mallee,  Eucalyptus  oleosa  (plate 
25b).  On  the  lower  slopes  of  the  higher  hills,  east  of  Saltia,  occur 
Casuarina  lepidophloia,  Cassia  sturtii,  Kochia  pyrmidata,  Senecio 
anethifolius,  and  Eucalyptus  odorata.  Still  farther  east  and  across  the 
high  valley  east  of  Saltia  are  thick  forests  of  mallee,  E.  odorata  and 
E.  oleosa,  and  with  the  mallee  were  found  Geigera  parvifiora,  Dodonosa 
lobulata,  Cassia  sturtii,  Hakea  leucoptera,  Pholidia  sp.,  and  others. 
The  vegetation  along  Saltia  Creek,  including  the  lowlands  on  either 
side,  possibly  flood-plain,  is  characterized  by  trees  of  good  size  and  in 
fair  abundance.  The  dominant  species  by  the  streamway  is  Eucalyptus 
rostrata  (plate  26a),  and  Callitris  robusta  is  also  fairly  common.  With 
these  species  there  occur  a  few  individuals  of  Acacia  iteaphylla. 


96  PLANT   HABITS   AND   HABITATS   IN   THE 

Sizes  and  Forms  of  Leaves  and  Phyllodia. 
Measurements  were  made  of  the  sizes  of  the  leaves  and  phyllodia 
of  some  of  the  woody  perennials  growing  about  Tarcoola  and  Port 
Augusta.  It  was  found  that  these  fall  into  two  well-marked  groups, 
namely,  those  relatively  wide  and  those  relatively  long.  In  the  former 
case  the  relation  of  width  to  length  is  about  2.2  to  1,  and  in  the  latter  it 
is  about  1  to  15.4.  The  average  breadth  of  the  leaves  and  phyllodia  is 
about  2.8  mm.  in  the  former  and  6.8  mm.  in  the  latter.  The  average 
length  is  42.8  mm.  and  14.8  mm.  in  the  two  classes  of  leaves  or  phyllo- 
dia, respectively.  The  foregoing  measurements  refer  to  Tarcoola 
plants  only.  So  far  as  those  from  Port  Augusta  are  concerned,  it  was 
found  that  the  narrow  tyipe  had  the  following  averages:  length,  66.3 
mm.;  breadth,  4.8  mm.,  giving  thus  a  ratio  of  length  to  breadth  of 
about  13.8  to  1.  A  noteworthy  feature  in  the  ecology  of  these  plants 
is  that  species  with  narrow  type  of  fohage  may  occur  both  along 
stream  ways,  where  the  water  conditions  are  relatively  good,  and  also 
away  from  the  washes,  and  hence  amid  more  arid  surroundings.  A 
more  detailed  account  of  the  sizes  and  form,  as  well  as  other  characters 
of  the  foliage  of  the  Port  Augusta  and  Tarcoola  plants,  appears  on 
pages  111  to  113. 

VEGETATION  AND  ENVIRONMENT  AT  QUORN. 

The  regions  represented  in  this  reconnaissance  of  the  most  striking 
features  in  the  perennial  vegetation  of  the  drier  portions  of  South 
Australia  are,  according  to  the  terminology  here  adopted,  desert,  arid, 
or  semi-arid.  Oodnadatta  and  the  Lake  Eyre  Basin  represent  the 
first;  Copley  and  the  southwestern  portion  of  the  state  the  second; 
and  Quorn  the  last.  To  the  latter,  however,  may  be  added  the  mallee 
region  around  Blanchtown.  There  is  thus  a  progressive  series  so  far 
as  the  rainfall  is  concerned.  Naturally,  and  in  a  manner  closely 
paralleling  the  increase  in  rainfall,  there  is  an  increase  in  the  amount 
of  vegetation,  with  a  gradual  creeping  in,  as  one  progresses  from  the 
more  arid  to  the  less  arid  regions,  of  forms  less  well  adapted  to  with- 
stand the  rigors  of  intense  aridity.  There  is  an  increase  in  the  number 
of  species  as  well. 

To  adequately  describe  as  a  whole  the  flora  of  any  of  these  regions, 
not  to  say  those  with  the  greatest  rainfall,  would  be  a  very  serious  un- 
dertaking. This,  as  I  have  already  pointed  out,  is  not  the  object  of 
this  study,  which  aims  rather  to  investigate  types  of  representative 
plants  and  their  adjustment  to  the  surroundings  in  which  they  are  to 
be  found.  Although  I  have  pointed  this  out  in  the  introductory  portion 
of  the  study,  it  seems  well,  in  order  that  there  can  be  no  misunderstand- 
ing, that  I  refer  to  it  again.  This  is  particularly  necessary,  inasmuch  as 
the  flora  at  and  about  Quorn  is  especially  rich  and  the  treatment  of  it 
to  follow  makes  no  pretense  of  completeness. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  97 

Quorn  is  situated  about  20  miles  to  the  east  of  Port  Augusta  and 
has  an  altitude  of  about  1,000  feet  above  that  place.  It  is  at  the  junc- 
tion of  the  railroad  leading  to  Port  Augusta  and  Western  Australia, 
on  the  one  side,  and  to  Copley,  Farina,  Maree,  William  Creek,  and 
Oodnadatta  in  the  far  north,  on  the  other.  The  country  between 
Copley  and  Quorn,  east  of  Lake  Torrens,  has  many  points  of  interest. 
Leaving  Copley,  which  is  situated  in  the  angle  where  the  Mount  De- 
ception Ranges  take  off  from  the  main  masses  of  the  Flinders,  the 
railway  goes  through  a  pass  with  rugged,  arid  hills  on  either  side  and 
emerges  on  the  Lake  Torrens  Plain,  over  which  it  passes  until  it  nears 
Hawker.  Here  it  enters  more  outhers  of  the  Flinders  Ranges  and, 
turning,  takes  a  more  southwesterly  direction,  climbing  somewhat, 
and  crossing  the  Willochra  Plain,  it  finally  gets  to  Quorn.  For  much  of 
the  distance  from  Copley  to  Quorn,  therefore,  the  picturesque  and 
abrupt  western  edge  of  the  Flinders  parallels  the  line  to  the  east, 
while  on  the  west  the  plain  stretches  into  the  haze  of  the  region  of 
Lake  Torrens.  On  the  Torrens  Plain,  halophytes  dominate,  but  species 
not  well  adapted  to  excessive  amounts  of  salts  are  to  be  seen  following 
water-courses  across  the  pkin.  The  presence  of  a  fairly  abundant 
vegetation  acts  to  protect  the  soil  for  the  most  part,  although  in 
places  moderate  winds  suffice  to  set  it  going,  much  to  the  discomfort  of 
the  traveler,  and  in  high  winds  the  amount  of  soil  so  transported  must 
be  very  great  indeed. 

In  the  Flinders  Ranges  between  Copley  and  Quorn  there  are  rela- 
tively high  summits,  the  effect  of  the  altitude  of  which  is  accentuated 
by  the  western  scarp  and  the  sudden  rise  from  the  plain.  There  are 
interesting  formations  in  the  Flinders  of  this  region — for  example,  the 
well-known  Wilpena  Pound,  which  has  resulted  from  a  circumclinal 
faulting  and  is  accessible  from  one  side  only.  The  mountains  here 
have  abundant  rains  and  hence  possess  rich  flora.  Species  of  Eucalyp- 
tus aie  said  to  attain  to  large  size  at  and  in  the  region  of  the  pound. 
The  Willochra  Plain,  which  the  raihoad  crosses  just  before  reaching 
Quorn,  is  an  alluvial  plaip  formed  by  delta  fans  from  the  mountain 
washes.  It  extends  from  Melrose  (to  the  south  of  Quorn)  to  Lake 
Torrens  and  is  in  part  subject  to  inundation  from  Willochra  Creek  and 
its  branches.  The  surface  of  the  plain  is  fairly  level  and  the  run-off 
following  rains  is  inconsiderable,  so  that  the  water  soaks  into  the 
ground  very  largely  where  it  falls.  The  drainage  of  the  plain  is  through 
Willochra  Creek  into  Lake  Torrens. 

Quorn  is  connected  with  the  plain  east  of  Spencer's  Gulf  by  Pichi 
Richi  Pass,  through  which  the  raihoad  goes  to  Poit  Augusta.  The 
altitude  of  the  pass  is  1,335  feet  and  it  is  about  6  miles  to  the  west  of 
Quorn. 

The  topography  about  Quorn  is  varied  and  interesting.  The  altitu- 
dinal  differences  are  relatively  great.  There  are  rugged  hills  and 
mountains  and  valleys,  narrow  in  the  hills  but  widening  as  they  de- 


98  PLANT   HABITS   AND   HABITATS   IN   THE 

bouch  on  the  eastern  plain.     Between  them  are  ridges,  often  very  long 
and  very  narrow. 

The  highest  summit  in  the  vicinity  of  Quorn  is  Mount  Brown 
(3,500  feet),  although  Devil's  Peak  is  about  as  high.  There  are  low 
mountains  just  north  of  the  village,  and  about  8  miles  north  Mount 
Arden  rises  fairly  precipitously.  Not  far  from  this  mountain  are  in- 
teresting gorges  in  the  main  mountain  mass  on  the  west.  At  one  of 
these  is  Depot  Flat,  where  there  is  an  interesting  glacial  till  of  pre- 
Cambrian  age,  and  another  is  Warren's  Gorge,  both  of  which  were 
kindly  shown  me  by  Mr.  Jensen,  engineer,  of  Quom.  The  valleys 
amid  these  hills  and  mountains  are  largely  under  cultivation,  but  the 
higher  land  is  used  for  grazing  purposes  only.  From  this  sketch  of  the 
general  features  of  the  topography  at  Quom  it  can  be  rightly  concluded 
that  the  village  is  very  picturesquely  situated. 

The  observations  on  the  flora  of  the  vicinity  of  Quorn  were  made  from 
the  various  roads  which  radiate  out  from  the  village,  so  that  it  will  be 
convenient  to  characterize  the  places  visited  by  reference  to  the  roads. 
So  far  as  possible,  I  have  retained  the  names  of  the  roads  in  conmion 
use,  but  in  one  or  two  instances,  when  I  did  not  know  the  name  com- 
monly used,  I  have  given  names  suitable  to  my  purpose.  The  roads 
are  as  follows:  To  the  north  of  Quorn  is  what  will  be  termed  the  Mount 
Arden  road,  which  goes  through  the  Flinders  at  this  point  to  the  Lake 
Torrens  Plain,  some  miles  beyond  Mount  Arden  itself.  The  Port 
Augusta  road  parallels  the  railway  and  goes  up  to  and  through  the 
Pichi  Richi  Pass.  The  Mount  Brown  road  goes  in  a  southwesterly 
direction  to  Mount  Brown,  passing  Devil's  Peak  to  the  south.  The 
latter  lies  between  the  two  roads  last  mentioned.  To  the  east  of  the 
town  the  Hawker  road  parallels  the  railway  to  and  across  the  Willochra 
Plain,  and  lying  south  of  this  main  road  are  two  others,  one  here  called 
the  Stephenston  road,  the  other  the  Melrose  road.  Both  of  these  go  to 
and  onto  the  Willochra  Plain,  the  former  running  east  and  west  along 
the  south  side  of  Quorn  Creek  and  its  terraces,  and  the  latter  going  at 
once  over  low  hills  to  the  plain.  Thus  there  are  about  six  main  roads 
leading  away  from  Quorn,  of  which  three  go  to  the  Great  Valley  Plain 
to  the  east,  and  three  into  and  between  the  mountains  on  the  north  and 
west  of  the  town. 

Although  the  rocks  about  Quorn  are  Cambrian,  as  the  rest  of  the 
Flinders  Ranges  mainly  are,  they  are  of  various  composition  and  the 
soil  derived  from  them  is  correspondingly  varied.  There  are  quartzite 
ridges  and  slate  hills,  the  latter  being  of  a  rounded  contour.  The  soil 
of  the  valleys  around  Quorn  seems  to  be  largely  clay  with  a  greater  or 
less  admixture  of  sand.  The  low,  rounded  hills  along  the  Melrose 
road  are  underlain  by  a  white  material  having  the  appearance  of 
travertine  limestone,  which  it  may  be.  Much  of  the  soil  of  the  Willo- 
chra Plain  is  fine  clay. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  99 

Climate. 

The  mean  annual  rainfall  for  Quorn  is  13.82  inches.  The  highest 
precipitation  recorded  was  25.77  and  the  least  7.43  inches.  The  mean, 
maximum,  and  minimum  amounts  of  rain  for  each  month  are  given 
in  table  2. 

It  will  be  seen  from  table  2  that  Quorn  is  in  the  belt  of  winter 
rains.  Beginning  to  fall  in  appreciable  amount  in  the  last  month  of 
autumn,  the  rains  are  maintained  through  the  winter  and  until  well 
into  the  spring,  only  about  30  per  cent  falling  during  the  warm  season. 
The  mean  rainfall  of  the  latter  is  4.18  inches.  This  is  very  little  more 
than  that  for  the  same  month  at  Copley,  which  is  3.82  inches,  or  45.4 
per  cent  of  the  whole.  Therefore,  the  rainfall  of  the  warm  season  at 
Quorn  is  relatively  and  actually  small  in  amount,  and  possibly  this 
gives  the  xerophytic  stamp  to  the  flora  of  the  region,  whereas  the 
relatively,  as  well  as  actually,  large  winter  rainfall  makes  possible 
an  abundant  vegetation.  Further,  it  is  this  which  makes  wheat- 
growing  without  irrigation  possible  in  the  region. 

Although  the  rainfall  at  Quorn  is  fairly  large,  it  has  certain  char- 
acteristics which  show  that  the  region  is  in  fact  semi-arid.  The  ratio 
of  driest  to  wettest  years  is  1  to  3.4.  In  a  humid  region,  as  for  example 
at  Hobart,  Tasmania,  this  ratio  is  much  less,  being  1  to  1.8.  At  Quorn 
the  year  having  the  greatest  precipitation  (1889)  followed  that  with 
the  least  precipitation.  However,  there  may  be  a  series  of  dry  or  wet 
years  when  successive  years  would  show  a  great  consistency. 

The  rainfall  on  the  Willochra  plain,  as  would  be  expected,  is  less  than 
at  Quorn.  For  example,  at  Bruce,  about  12  miles  southeast  of  Quorn 
and  on  the  western  side  of  the  plain,  the  annual  precipitation  is  9.88 
inches.  In  closer  relationship  to  the  high  mountains,  as  at  Mount 
Brown,  Melrose,  and  Wilmington,  the  precipitation  is  greater  than  at 
Quorn.  The  mean  for  the  three  places  is  17.23,  23.1,  and  18.23  inches, 
respectively.  The  rainfall  on  the  upper  slopes  of  Mount  Brown  and 
Mount  Remarkable  must  be  considerably  more  than  that  recorded 
for  stations  at  their  base. 

I  have  not  seen  data  on  the  temperature  at  Quorn,  nor  for  any  sta- 
tion near,  but  the  temperature  at  Yongala,  distant  about  65  miles, 
may  be  useful  as  illustrating  certain  main  features  of  the  temperature 
conditions  of  the  general  region.  The  rainfall  at  Yongala  is  almost 
the  same  in  amount  as  at  Quorn,  and  the  place  has  a  considerable 
elevation.  In  a  sense,  therefore,  the  two  are  comparable.  The  fol- 
lowing is  a  summary  of  the  conditions  at  Yongala :  Mean  maximum, 
69.2°;  mean  minimum,  46°;  mean  temperature,  59.6°;  highest  maxi- 
mum, 107.6°;  lowest  minunum,  19.8°  F.  The  mean  diurnal  range  is 
24.9°  and  the  greatest  daily  range  recorded  at  the  station  is  50.7°  F. 

When  the  preceding  temperature  data  are  compared  with  those 
for  Farina,  as  representing  Copley,  for  example,  it  is  seen  that  the 


100  PLANT   HABITS   AND   HABITATS   IN   THE 

latter  station  is  hotter  in  summer  and  colder  in  winter  and  that  the 
mean  annual  temperature  is  nearly  6°  F.  higher  than  at  Yongala. 
Moreover,  the  mean  diurnal  range  is  nearly  4°  F.  higher  at  Farina, 
although  the  maximum  diurnal  range  at  that  place  is  but  little  above 
that  given  for  the  more  southern  station.  A  somewhat  similar  rela- 
tion, possibly  less  marked,  may  perhaps  exist  between  Farina  and 
Quorn.  Thus,  it  will  be  seen,  Quorn  has  cool  winters  and  hot  summers, 
with  occasionally  very  high  temperatures. 

A  characteristic  of  the  temperature  of  the  region  which  should  be 
emphasized  is  its  great  daily  variation.  This  feature,  which  is  well 
marked  in  dry  regions,  is  of  undoubted  importance  in  its  effect  on 
plants.  An  instance  can  be  given  which  can  not,  unfortunately,  be 
supported  by  complete  data.  In  mid-October  1918,  the  day  tempera- 
tures at  Quorn  were  most  agreeably  cool,  although  it  was  the  middle 
of  spring.  Green  growth  and  fresh  flowers  were  everywhere  and  there 
was  Httle  to  suggest  the  brown  hills  of  the  summer  to  come.  Particu- 
larly the  roadsides  in  places  were  masses  of  blue  from  the  flowers  of 
the  introduced  Echium  platagineum.  One  day  late  in  the  month 
the  wind  turned  to  the  north  and  brought  with  it  the  high  tempera- 
tures and  the  dry  air  of  the  Lake  Torrens  Basin.  Rising  to  96°  F.  in  a 
few  hours,  and  with  as  sudden  a  drop  in  the  relative  humidity,  the 
arid  conditions  swept  over  the  country  like  a  flame,  drying  and  turning 
brown  in  a  comparatively  brief  time  most  of  the  annual  vegetation  and 
severely  testing  the  resistance  of  the  perennials. 

Vegetation  and  Habitat. 

The  flora  of  the  Quorn  region  is  rich  in  species  and  in  individuals. 
The  mountains  are  clothed  with  a  wealth  of  shrubs  and  small  trees, 
only  the  big  outcropping  rocks,  often  picturesquely  serrated  against 
the  sky,  being  destitute  of  vegetation,  and  the  hillsides  and  floors  of 
the  valleys  are  thickly  covered  with  trees,  shrubs,  and  lesser  plants. 
Thus  the  vegetal  aspect  of  the  region  is  quite  different  from  what  was 
seen  at  Copley  or  in  southwestern  South  Australia,  with  about  5  inches 
less  rainfall,  and,  as  would  be  expected,  markedly  different  from  that 
at  Oodnadatta.  It  in  fact  compares  well  with  the  vegetation  farther 
south,  where  the  rainfall  is  much  greater.  Quorn  has  been  settled 
many  years.  In  earlier  times  the  woody  plants  must  have  been  much 
more  numerous  than  at  present  and  more  generally  distributed ;  but 
otherwise  the  vegetation  is  probably  not  greatly  changed  by  the  advent 
of  the  white  man  and  his  varied  activities,  and  as  a  whole  it  probably 
well  represents  plant  adjustments  under  relatively  arid  conditions. 

The  leading  habitats  in  the  vicinity  of  Quorn  include  the  higher 
mountains,  as  Devil's  Peak  and  Mount  Arden;  the  lower  ridges, 
some  of  which  reach  out  to  the  Willochra  Plain,  the  valleys  between 
these  ridges,  the  Willochra  Plain,  and  finally  Quorn  Creek  and  its 


ARID    PORTIONS   OF   SOUTH   AUSTRALIA.  101 

tributaries.  No  attempt  will  be  made  to  describe  the  plants  of  these 
habitats,  all  of  which,  except  the  high  mountains,  were  visited;  but, 
as  previously  indicated,  only  such  vegetational  features  as  seemed 
most  interesting  will  be  taken  irito  account,  with  general  reference  to 
the  plants  as  a  whole;  and  the  situation  of  the  habitats  treated  will 
be  located  by  means  of  reference  to  roads  going  out  from  the  village. 

Vegetation  of  the  Valleys  and  of  Willochra  Plain. 

So  far  as  can  be  judged  from  a  very  superficial  view  of  the  Willochra 
Plain  in  the  vicinity  of  Quorn,  and  apart  from  the  streamways  passing 
through  it,  saltbushes  of  whatever  sort  constitute  a  prominent  part 
of  its  natural  vegetation.  There  is,  however,  much  grass  in  places, 
particularly  where  the  plain  extends  toward  Quorn  between  the  tongues 
of  the  low  ridges,  and  as  one  goes  up  the  valleys  from  the  open  plain 
and  they  become  higher  and  narrower,  the  woody  flora  becomes  of 
increasing  importance. 

The  leading  habitats  as  given  in  a  preceding  paragraph  are  in  the 
main  fairly  distinct,  but  not  always  so.  Where,  for  example,  the 
plain  narrows  into  the  pass  on  the  Port  Augusta  road,  they  rise  to 
meet  the  hills  and  the  three  are  merged,  and  in  other  places  the  hills 
may  melt  insensibly  into  the  valley.  Such  a  place  occurs  along  the 
Mount  Arden  road  at  about  2  or  3  miles  north  of  Quorn.  Here  the 
valley  is  somewhat  rolling  and  there  are  remains  of  the  original  vegetal 
covering.  By  the  roadside  one  sees  several  woody  perennials,  shrubs 
largely,  of  which  Templetonia  egena  is  the  most  numerous.  This  species 
occurs  generally  along  the  valley  floor  near  Quorn  and  is  very  abundant 
in  unused  fields.    It  has  a  strict  habit  of  growth  and  is  leafless. 

This  shrub  occurs  in  fairly  loose  groups  which  result  from  vegetative 
propagation  in  the  following  manner:  A  portion  of  the  root-system 
is  superficial  and  from  some  of  the  largest  of  such  roots,  and  at  a  dis- 
tance of  50  to  100  cm.  from  the  parent  plant  they  may  give  rise  to 
shoots.    These  eventually  become  independent  plants. 

Acacia  calamijolia  is  another  roadside  shrub.  This  species  has 
narrow  filiform  phyllodia,  which  are  fairly  numerous  and  about  7  cm. 
in  length.  It  occurs  in  fairly  close  aggregations,  making  a  small  but 
dense  and  low  scrub  mass.  An  examination  of  the  root-system  showed 
that  there  are  no  prominent  superficial  laterals,  as  in  the  last-named 
species,  but  that,  on  the  other  hand,  the  main  tap-root  is  prominently 
developed.  The  species  occurs  in  unused  fields,  as  well  as  by  the  road- 
sides.    Among  other  species  growing  near  are  the  following : 

Acacia  hakeoides.  Cassia  eremophila.  Helichrysum  spiculatum. 

sentis.  Cassia  sturtii.  Senecio  anethifolius. 

sublanata.  Eutaxia  empetrifolia.  Templetonia  aculeata. 

Bursaria  spinosa.  Glycine  clandestina. 


102  PLANT   HABITS   AND    HABITATS   IN   THE 

Acacia  hakeoides  is  marked  by  its  upright  phyllodia,  5  to  10  cm.  in 
length  and  about  4  mm.  wide.  A.  sentis  is  a  small  tree  with  phyllodia 
about  20  mm.  in  length.  It  has  spinescent  stipules.  A.  suhlanata 
(plate  27a)  is  also  a  small  shrub,  fairly  numerous,  characterized  by 
having  phyllodia  triangular  in  form  and  about  2  mm.,  in  diameter. 
Bursaria  spinosa  is  a  small  shrub,  1.5  to  2  meters  in  height  and  with 
leaves  occurring  in  groups.  The  leaves  are  fairly  numerous  and  are  2 
to  4  cm.  in  length.  The  Quorn  species  appears  not  to  be  armed. 
Cassia  eremopMla,  a  shrub,  is  characterized  by  linear  leaflets  which 
arise  from  a  phyllode-like  leaf-stalk.  In  C.  sturtii  the  leaflets  are 
numerous,  6  to  10,  and  are  about  10  mm.  in  length.  The  leaves  of 
this  species  can  also  be  said  to  be  abundant.  Eutaxia  empetrifoUa 
(plate  27b)  is  a  low  shrub  with  linear  leaves,  about  3  mm.  long,  but 
numerous.  Glycine  clandestina,  a  twining  herb  with  slender  leaflets, 
was  one  of  the  very  few  climbers  which  were  seen  at  Quorn.  Helichry- 
sum  spiculatum  is  a  leafy  herb  clothed  with  cottony  pubescence  and  is 
fairly  abundant.  Senecio  anethifolius  is  a  small  shrub  with  numerous 
linear  lanceolate  leaves,  and  is  also  rather  abundant.  Templetonia 
aculeata  is  a  low,  rigid  shrub  with  simple  leaves,  about  10  mm.  in  length. 
It  has  prickly  stipules  and  thus  is  one  of  the  few  armed  species  in  the 
vicinity  of  Quorn. 

All  of  the  species  whose  salient  characters  have  just  been  sketched 
were  growing  in  vacant  fields  and  by  the  roadside  about  4  miles  north 
of  Quorn  along  the  Mount  Arden  road.  The  valley  at  this  place  is 
fairly  level,  but  as  one  goes  farther  north  it  ascends  somewhat,  be- 
comes narrower,  and  by  the  time  Mount  Arden  is  reached,  about  4 
miles  farther,  trees  characteristic  of  the  higher  hills  are  encountered. 
Here,  and  especially  at  Warren's  Gorge  (plate  26b),  one  finds  small 
forests  of  the  pine,  Callitris  rohusta,  at  a  place  where  a  small  stream 
breaks  through,  making  the  only  means  of  access  to  the  rounded 
slate  hills  beyond.  The  main  ridge  of  the  mountain  through  which 
the  gorge  runs  rises  steeply  at  one  side  and  the  shale  hills  ascend 
gradually  on  the  other.  The  latter  is  the  habitat  of  Callitris  rohusta, 
but  it  also  occurs  on  the  mountain  itself.  On  certain  of  the  slopes, 
however,  mallee  {Eucalyptus  odorata  and  E.  oleosa)  occur  on  the  upper 
reaches,  while  the  middle  of  the  slope  is  occupied  by  Zygophyllum  sp., 
below  which  is  Callitris,  reaching  down  to  Eucalyptus  leucoxylon  var. 
pauperita  by  the  stream.  There  are  no  shrubs  and  very  little  grass 
or  other  annuals  in  the  Callitris  community,  which  extends  close  to 
the  stream.  Somewhat  upstream  from  Warren's  Gorge,  and  growing 
on  tumbled  rocks  low  on  the  hillside  above  it,  is  Sarcostemma  australe. 
This  is  a  leafless  species  of  Asclepiadeae  which  here  hangs  and  sprawls 
over  the  rocks  with  a  most  weird  effect. 

At  certain  places  along  the  Mount  Arden  road,  which  passes  up  a 
narrowing  and  ascending  valley  with  characteristic  changes  in  the 
vegetation  as  above  suggested,  one  finds  patches  of  the  introduced 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  103 

and  escaped  annual  Echium  plantagineum;  but  it  is  most  abundant 
nearer  Quorn,  especially  along  the  Port  Augusta  road.  It  constitutes 
the  dominant  species  of  fairly  large  and  isolated  areas.  Various 
grasses,  however,  make  up  the  largest  number  of  the  herbaceous 
flora  by  which  the  valley  floor  near  the  village  is  thickly  covered. 
How  many  of  these  are  native  and  how  many  are  introduced,  however, 
was  not  determined  by  me;  but  it  seems  possible  that  at  least  on  the 
lowest  portions  of  the  valleys  there  must  always  have  been  a  grassy 
vegetation,  so  that  the  grassland-forest  formation  of  the  regions  of  a 
relatively  large  rainfall,  as  in  portions  of  the  Mount  Lofty  Ranges 
near  Adelaide,  can  be  said  to  be  represented  at  this  place. 

One  of  the  most  striking  communities  on  the  Mount  Arden  road  is 
that  of  the  mallee,  an  example  of  which  lies  about  2  miles  north  of 
Quorn.  The  dominant  species  of  the  mallee  scrub  are  Eucalyptus 
odorata  and  E.  oleosa.  These  are  small  trees  with  a  shrubby  growth- 
habit  and  the  canopy  top  characteristic  of  the  mallee  (plate  26c). 
The  scrub  is  fairly  dense  and  the  number  of  species  comparatively 
large.  The  following  list,  which  is  doubtless  far  from  complete,  com- 
prises those  most  conspicuous : 

Acacia  iteaphylla.  Eucalyptus  odorata.  Loranthus  pendulus. 

oswaldii.  oleosa.  Myoporum  platycarpum. 

pycnantha.  Eutaxia  empetrifolia.  Olearia  pannosa. 

Cassia  sturtii.  Exocarpus  aphylla.  pimeleoides. 

Cassinia  aculeata.  spartea.  Pittosporum  phillyraeoides. 

Dodonaea  attenuata.  Hakea  leucoptera.  Rhagodia  parabolica. 

Eremophila  brownii.  Indigofera  australis  var.  minor.      Triodia  irritans. 

oppositifolia.       Jasminum  lineare.  Zygophyllum  billardieri. 

When  examined  somewhat  in  detail,  the  scrub  reveals  conditions 
rather  different  from  those  before  seen,  as,  for  example,  at  Copley. 
The  larger  number  of  individuals  indicates  better  water  relations  than 
at  stations  farther  north  or  along  the  East- West  Railway.  In  addition, 
a  study  of  the  leaf-surface  would  probably  show  that  the  transpiring 
area  is  considerably  larger  as  well.  In  certain  other  regards,  however, 
a  similarity  exists.  For  instance,  there  is  little  shade  in  the  scrub  in 
any  of  the  dry  localities  seen,  including  Quorn.  The  mallee  scrub  at 
Quorn  is  here  compared  with  the  mallee  scrub  in  the  Mount  Deception 
Range  west  of  Copley.  Should  comparison  be  made  with  the  hill- 
slope  community  as  a  whole  at  Copley,  all  of  these  conditions  and  dif- 
ferences would  be  greatly  increased. 

Each  of  the  three  species  of  Acacia  observed  in  the  mallee  scrub 
has  prominent  phyllodia,  but  those  of  A.  pycnantha,  the  "golden 
wattle,"  are  actually  large,  measuring  about  13  cm.  in  length  by  about 
2  cm.  in  width  (plate  27c),  and  they  are  numerous  on  the  small  tree 
also.  This  species  is  not  present  in  large  numbers  in  the  scrub,  al- 
though, as  will  appear  below,  it  forms  a  small  grove  on  the  river  bot- 
toms near  the  village.    It  occurs  in  the  more  moist  portion  of  the  state, 


104  PLANT  HABITS  AND  HABITATS  IN  THE 

as  in  the  Mount  Lofty  Ranges  near  Adelaide,  so  that  its  presence  at 
Quorn  suggests  that  that  place  may  be  regarded  as  being  on  the  transi- 
tion line  between  the  dry  north  and  the  humid  south.  This  view  is 
substantiated  by  rainfall  statistics  also,  as  well  as  by  other  facts 
touching  plant  distribution. 

Cassia  sturtii  is  present  in  small  numbers.  The  leaflets  are  6  to  10 
in  number,  and  both  the  narrower  and  the  broader  leaved  forms  are 
to  be  found  in  the  scrub.  At  Quorn  it  forms  a  shrub  about  1  to  1.5 
meters  high  and  ranks  with  the  golden  wattle  in  the  brilliance  of  its 
flower.  The  species  has  the  appearance  of  having  a  greater  leaf  sur- 
face than  at  Copley. 

As  above  given.  Eucalyptus  odorata,  the  mallee,  is  a  small  tree, 
about  8  to  10  meters  high  at  Quorn,  and  has  the  so-called  "mallee" 
habit  of  growth — that  is  to  say,  in  place  of  there  being  one  main  shoot 
only,  many  shoots  of  equal  rank  and  of  approximately  equal  length 
spring  from  a  thickened  base.  Each  shoot  ends  in  a  number  of  small 
branches  of  unequal  length  which  bear  only  leaves.  The  general  canopy 
effect  is  indicated  in  plate  26c.  The  leaves  of  E.  odorata,  as  well  as  of 
E.  oleosa,  are  relatively  small.  They  are  8  to  12  cm.  long  and  usually 
less  than  a  centimeter  wide. 

Of  the  two  species  of  Eremophila,  E.  brownii  is  the  most  widely 
distributed  in  South  Australia.  It  was  seen  at  Oodnadatta  and  at 
Copley  and  occurs  in  the  southern  and  western  portions  of  the  state 
as  well.    The  leaves  are  linear  and  2  to  3  cm.  in  length. 

Exocarpus  spartea  and  E.  aphylla  are  not  common  in  the  mallee  scrub, 
although  the  latter  is  fairly  abundant.  The  latter  is  a  shrub  2  to  4 
meters  high  and  with  its  leafless  branches  is  very  striking.  E.  spartea 
has  linear-subulate  leaves,  which,  however,  do  not  conceal  the  broom- 
like branches.  The  leaves  of  this  species  appear  to  fall  away  easily, 
so  that  upon  the  advent  of  dry  seasons  the  shoots  are  probably  bare. 
Eutaxia  empetrifolia  is  a  small,  weak  shrub  with  minute  linear  leaves. 

Another  species  common  in  the  scrub  is  Dodoncea  attenuata;  this  has 
a  dense  shoot  whose  leaves  and  fruit  are  covered  with  a  resinous 
substance.  Hakea  leucoptera,  which  was  found  at  Copley  also,  is 
rather  abundant  on  the  outskirts  of  the  scrub  and  in  the  adjacent  open 
fields.  Hakea  is  a  shrub,  1.5  to  2.5  meters  high,  which  occurs  in  open 
colonies.  A  portion  of  the  root-system  of  the  species  lies  close  to  the 
surface  of  the  ground  and  from  such  roots  daughter  shoots  spring  up, 
reproducing  the  plant  vegetatively  (plate  28b).  From  the  frequent 
occurrence  of  Hakea  in  groups,  as  noted,  it  seems  that  this  is  a  common 
way  of  its  propagation. 

Of  the  other  species,  Pittosporum  phillyrceoides  is  one  of  the  most 
interesting.  This  is  a  small  tree  with  drooping  branches  and  leaves 
about  15  cm.  long  by  5  to  8  mm.  wide.  In  the  mallee  scrub  there 
is  also  a  fairly  thick  growth  of  Triodia  irritans.  Loranthus  pendulus 
occurs  fairly  abundantly  on  Eucalyptus  oleosa  in  the  scrub.    However, 


ARID    PORTIONS   OF    SOUTH    AUSTRALIA.  105 

the  Loranthaceae  are  not  nearly  so  common  here  or  elsewhere  about 
Quorn  as  at  Copley. 

Near  the  Port  Augusta  road  and  about  2  miles  west  of  Quorn  are 
other  mallee  scrubs  in  which  there  appear  to  be  fewer  species  than  in 
the  scrub  just  described.  Low  ridges,  extending  from  the  higher  hills 
and  mountains  to  the  Willochra  Plain  (plate  28a),  are  covered  with 
Eucalyptus  oleosa  and  E.  odorata  as  the  dominant  species.  Here  were 
also  found  Dodoncea  bursarifolia  and  Pholidia  santalina  (syn.  Ere- 
mophila)  (plate  23a). 

Where  the  valley  ascends  to  Pichi  Richi  Pass,  on  either  side  of  the 
road  are  hills  a  portion  of  which,  as  just  described,  bear  mallee  scrub; 
but  some  of  the  hills  bear  scattered  low  shrubs  and  are  heavily  covered 
with  grass.  Of  the  shrubs.  Acacia  continua  (plate  23c)  is  possibly  the 
most  common,  although  it  occurs  but  sparingly.  Widely  scattered 
specimens  of  Casuarina  sp.  also  occur,  but  the  grasses  Triodia  irritans, 
the  porcupine  grass  or  Spinifex,  and  Trichiniurn  spathulatum  are  the 
dominant  species. 

Somewhat  higher  in  the  valley  the  mallee  and  other  species  of  Euca- 
lyptus come  to  the  valley  floor  and  here  the  grass  is  absent.  It  seems 
possible,  although  this  will  require  verification,  that  the  mallee-covered 
ridges  above  referred  to  are  shale,  while  the  grassy  hills  are  quartzite. 
In  the  vicinity  of  Quorn,  so  far  as  my  observation  went,  it  appeared 
that  bunch-grass  and  Casuarina  were  both  found  where  there  was  an 
outcropping  of  the  latter.  As  an  example  of  this,  the  vegetation  of 
the  quartzite  ridge  east  of  the  Mount  Arden  road  and  about  3  miles 
north  of  Quorn  may  be  given. 

Vegetation  of  Low  Hills. 
Mention  has  already  been  made  that  the  low  ridges  which  extend 
in  a  generally  easterly  direction  to  the  Willochra  Plain  from  the  higher 
hills  and  mountains  are  in  part  at  least  covered  with  mallee  and  that 
certain  of  the  hills  near  the  Pichi  Richi  Pass,  on  the  Port  Augusta 
road,  are  grass  hills  on  which  there  are  scattering  woody  perennials. 
The  vegetation  of  three  other  hills  or  ridges  should  be  mentioned. 
Of  these,  the  ridge  last  referred  to  as  being  along  the  eastern  side  of 
Mount  Arden  road  has  vegetational  features  of  interest.  On  the 
western  slope  is  a  heavy  covering  of  bunch-grass  growing  very  thickly, 
Triodia  irritans  and  Trichinium  spathulatum,  with  a  few  and  scattering 
specimens  of  "mallee"  and  Xanthorrhcea  semiplana  (plate  28c).  Near 
the  summit  of  the  ridge  the  grass  becomes  more  scattering  and  Xanthor- 
rhcea semiplana  occurs  in  considerable  numbers.  On  the  top,  mallee 
dominates  the  woody  perennials,  although  CalUstemon  teretifolius  also 
occurs  (plate  23b).  Somewhat  lower  on  the  ridge  and  on  the  southern 
slope  mallee  ceases  and  Casuarina  stricta  is  met.  Whether,  as  may  be 
possible,  the  distribution  of  the  mallee  is  coincident  with  the  change 
from  quartzite  to  shale  was  not  determined. 


106  PLANT   HABITS   AND   HABITATS   IN   THE 

The  Melrose  road  passes  over  hills  on  its  way  to  the  western  edge 
of  the  Willochra  Plain.  These  hills,  at  least  in  part,  appear  to  be 
delta  fans  from  the  main  uplift  farther  to  the  west,  and  in  part  to  be 
eastern  ends  of  low  ridges  which  reach  to  the  western  higher  hills. 
Within  reach  of  the  road  a  considerable  variety  of  vegetation  is  to  be 
found,  of  which  may  be  mentioned  the  Casuarina  scrub  about  4  miles 
east  and  south  of  Quorn.  The  vicinity  of  the  scrub  is  largely  used  at 
present  in  agricultural  operations,  but  there  have  been  left,  apparently 
little  touched,  several  acres  of  "oak"  land  and  a  small  contiguous 
area  containing  other  native  vegetation.  The  Casuarina  scrub  is  an 
open  growth  with  Casuarina  stricta  predominating.  The  species  here 
forms  a  small  tree  3  to  5  meters  high.  It  reproduces  vegetatively 
from  shoots  which  arise  from  superficial  roots.  Another  species 
connnon  in  the  Casuarina  scrub,  and  which  reproduces  in  a  similar 
manner,  is  Templetonia  egena. 

In  addition  to  the  above  the  following  occur  in  the  same  community: 
Acacia  calamifolia  (plate  23d),  A.  oswaldii,  Exocarpus  aphylla,  Hakea 
leucoptera,  Heterodendrum  olecefolium,  Lycium  australe,  Nitraria  schoeheri, 
and  Triodia  irritans.  Besides  these  species  there  is  "sandal-wood," 
probably  Pittosporum  phillyroeoides,  which  occurs  sparingly. 

Inasmuch  as  some  of  the  more  obvious  and  interesting  features  of 
all  of  these  species  have  been  commented  on  in  the  preceding  pages, 
further  description  is  not  necessary.  It  will  be  noted,  however,  that 
three  of  the  species,  including  Hakea  leucoptera,  reproduce  vege- 
tatively from  the  roots  (plate  30c).  The  grass,  Triodia,  is  poorly 
represented  and  the  floor  of  the  scrub  is  fairly  clean.  The  species 
above  Hsted  are  not  equally  distributed  throughout  the  scrub,  but  a 
portion  occur  on  the  edge  of  the  Casuarina  community  more  plentifully 
than  in  the  center,  as,  for  example.  Acacia  oswaldii,  Hakea  leucoptera, 
Heterodendrum  olecefolium,  and  Nitraria  schceberi.  Here,  however,  as 
in  certain  other  places  in  the  vicinity  of  Quorn,  the  possibility  enters 
that  the  primitive  conditions  may  have  changed  through  the  agency 
of  man.  It  is  impossible  at  this  time  to  say  whether,  for  example, 
the  Casuarina  might  have  been  removed  from  the  latter  scrub  or 
whether  it  never  occurred  there. 

In  the  sketch  of  the  physiography  of  the  Quorn  vicinity  mention 
was  made  that  the  Willochra  Plain  is  continued  as  narrowing  valleys 
toward  the  higher  mountains.  Between  these  valleys,  and  near  where 
they  debouch  onto  the  plain,  are  low  hills,  the  terminations  of  those 
which  reach  out  from  the  high  land  west  of  the  village.  For  most  of 
their  course  the  hills  are  covered  with  a  scrub  of  some  sort,  as  has  been 
described,  but  at  their  plain-ends  the  condition  is  quite  different. 
Here  there  is  a  scattering  population  of  "blue  bush,"  mainly  Kochia 
sedifolia.    At  the  base  of  the  ridges  other  halophytes  occur  and  espe- 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  107 

cially  by  the  unimportant  washes  are  scattering  specimens  oi  Acacia  sentis. 
Strictly  speaking,  the  latter  species  belongs  rather  to  the  valley  than  to 
the  hill  flora. 

Vegetation  of  the  Washes. 

It  has  been  remarked  that  at  Quorn  there  is  frequently  no  sharp 
distinction  between  valley,  hill,  and  stream-plain,  but  that  in  places 
the  flora  of  the  three  may  merge,  even  if  in  others  they  are  quite  sepa- 
rate. This  is  possibly  less  true  of  the  vegetation  of  the  streamways 
than  of  the  other  formations.  The  characteristic  species  of  the  streams 
is  Eucalyptus  leucoxylon  var.  pauperita.  This  is  strictly  limited  to 
streams.  It  is  a  good-sized  tree,  becoming  about  7.6  meters  in  cir- 
cumference (plate  30b).  By  the  low  banks  along  the  washes,  which 
are  dry  most  of  the  year,  are  other  species  which  also  rarely,  or  never, 
occur  elsewhere.  For  example.  Acacia  pycnantha  forms  a  small  thicket 
by  the  wash  near  the  Mount  Brown  road  about  3  miles  southwest  of 
Quorn  (plate  30a),  but  there  are  no  other  species  of  woody  plants  here. 

Root  Characters. 

Some  observations  were  made  on  the  root-habits  of  the  mallees. 
Eucalyptus  oleosa  and  E.  odorata,  and  of  the  large  gum,  E,  leucoxylon 
var.  pauperita,  of  the  washes.  The  former  was  especially  studied  in 
the  small  mallee  community  about  3  miles  north  of  Quorn.  Here  a 
narrow  wash  runs  by  the  edge  of  the  scrub,  where  the  soil  is  fairly 
coarse  and  where  rock  underlies  it  to  a  depth  of  about  a  meter;  it  was 
found  that  the  tap-root  was  poorly  developed,  but  that  there  were 
numerous  radiating  superficial  roots.  In  a  typical  specimen  there  are 
about  12  main  laterals  of  this  character  which  are  placed  23  to  45  cm. 
beneath  the  surface  (plate  31a)  .  Many  roots,  about  2  mm.  in  diameter, 
arise  near  the  bases  of  the  large  laterals  and  go  directly  down. 

At  another  place,  by  the  Port  Augusta  road  and  about  4  miles 
west  of  Quorn,  a  fairly  deep  wash  also  exposes  roots  of  mallees  growing 
along  its  side.  Here  the  wash  is  about  2  meters  deep  and,  although 
there  does  not  appear  to  be  rock  to  limit  possible  root  penetration,  all 
of  the  species  had  the  superficial  type  of  roots  well  developed.  In 
one  instance  a  root  was  traced  1 1  meters  from  the  base  of  the  tree,  and 
at  a  distance  of  7  meters  it  had  a  diameter  of  2.5  cm.  In  another  case, 
after  having  extended  2  meters  from  the  tree  close  to  the  surface  of 
the  ground,  the  horizontal  root  sent  a  branch  straight  down.  This 
was  about  three  times  the  diameter  of  the  parent  root  and  was  traced 
to  a  depth  of  2  meters.  The  horizontal  roots  were  found  to  lie  usually 
within  20  cm.  of  the  surface  of  the  ground. 

Owing  to  its  usual  position  in  the  bottom  of  the  washes,  the  roots  of 
the  gums  here  are  rarely  much  exposed,  but  it  is  usual  for  several 
prominent  roots  to  take  their  origin  close  to  the  surface  of  the  ground; 
in  one  instance  it  was  found  that  such  roots  may  extend  for  a  long 
distance  near  the  surface.    By  the  streamway,  for  example,  about  a 


108  PLANT   HABITS   AND   HABITATS   IN   THE 

mile  beyond  Warren's  Gorge,  where  there  are  many  large  specimens 
of  gum,  probably  Eucalyptus  leucoxylon  var.  pauperita,  there  is  at 
one  place  a  group  of  superficial  roots  which  are  exposed  for  a  distance 
of  about  16  meters  and  probably  extend  much  farther  (plate  31b). 
These  were  situated  about  20  cm.  beneath  the  surface  of  the  ground. 

MALLEE  AND  THE  MALLEE  REGIONS. . 

The  mallee  scrub  is  one  of  the  largest  and  most  distinctive  plant 
formations  of  South  Australia.  The  term  includes  species  of  Eucalyp- 
tus of  especial  habit  of  growth  which  may  or  may  not  be  obligate. 
In  the  mallee  the  stem  is  shortened  into  a  large  bulbous  base,  into 
which  the  enlarged  root-crown  insensibly  merges,  and  from  this  woody 
mass  there  spring  branches,  usually  of  about  equal  length,  which  bear 
leaves  at  their  tips.  Typical  mallees  thus  have  a  rounded  shoot, 
canopy-like,  and  the  general  effect  is  that  of  large  shrubs.  Among 
the  mallees  with  consistent  habit  are:  Eucalyptus  bicolor,  E.  caly- 
cogona,  E.  dumosa,  E.  goniocalyx,  E.  incrassata,  and  E.  oleosa. 

Eucalyptus  odorata  is  one  of  the  species  with  tree  habit  which  can 
assume  the  mallee  form  under  appropriate  conditions.  The  enlarged 
base  of  the  mallee  often  is  of  very  large  size.  Thus  Maiden  (1904: 93) 
states  that  it  becomes  as  much  as  9  feet  in  diameter  where  the  con- 
ditions are  favorable  for  its  development.  The  base  is  flattened  and  is 
firmly  planted  and  held  in  the  soil  by  the  numerous  roots,  most  of 
which  are  superficial  and  extend  outward  for  several  meters.  The 
bulbous  base  is  often  so  large  that  it  will  hold  the  shoot  upright  even 
when  all  of  the  roots  are  removed.  It  constitutes  a  notable  organ  for 
the  storage  of  water.  Maiden  says  that  the  base  may  be  so  full  of 
moisture  that  it  would  be  an  almost  endless  task  to  attempt  burning 
it  out.  When  finally  dry,  however,  the  mallee  "root"  becomes  of  value 
as  a  fuel  and  is  largely  used  for  this  purpose. 

The  mallees  occur  in  regions  with  winter  rains,  although  the  total 
amount  of  precipitation  may  vary  considerably  (Osborn,  1914). 
Thus,  in  regions  of  the  mallee  the  rainfall  may  range  from  about  9 
to  19  inches.  It  was  seen  in  the  mountains  west  of  Copley,  in  the 
sandhill  region  at  Ooldea,  near  Saltia,  and  at  Quorn.  At  Ooldea  the 
mallee  is  growing  under  a  9-inch  rainfall,  but  at  the  other  places  it  is 
more  than  this,  and  a  relatively  large  rainfall  (or  at  least  relatively 
good  water  relations)  is  apparently  a  prerequisite  to  the  attainment 
of  the  largest  growth  of  the  mallee. 

In  the  northern  or  central  portions  of  the  state  there  are  large  com- 
munities of  mallee,  but  its  largest  development  is  attained  in  the 
southern  part,  especially  on  the  bottoms  of  the  Murray  River  and  in 
the  region  to  the  west  of  Spencer  Gulf.  It  was  seen  by  me  west  of 
the  Murray  River,  between  Blanchtown  and  the  highlands  which 
border  the  Murray  Basin  on  the  west. 


ARID    PORTIONS    OF    SOUTH    AUSTRALIA.  109 

Physical  and  Climatic  Features. 

The  region  west  of  Blanchtown,  which  Hes  on  the  western  bank  of 
the  Murray  River,  is  nearly  level.  However,  it  has  the  appearance, 
although  whether  this  is  true  in  fact  was  not  learned,  of  rising  as  one 
approaches  the  river. 

In  this  characterization  of  the  region  Howchin  (1909:95)  says: 

"  The  greatest  development  of  the  coastal  plains  in  South  Australia  is  in 
the  southeast,  between  the  central  highlands  and  the  Victorian  border.  It  is 
often  spoken  of  in  three  sections :  The  Murray  Flats,  between  the  ranges  and 
the  River  Murray;  the  Ninety-Mile  Desert,  between  the  river  and  the 
Victorian  border,  by  the  old  stock  routes;  and  the  South-East  or  most  south- 
erly section.  The  physical  features  throughout  are  very  uniform.  Gently 
undulating  ground,  with  a  few  more  prominent  ridges ;  light,  sandy  soil  which 
frequently  changes  to  a  travertine-limestone  crust." 

The  Murray  Fkts,  which  were  visited,  forms  a  part  of  the  great 
Murray-Darling  Basin,  which  is  the  most  extensive  river  basin  on  the 
continent.  This  basin  probably  should  be  considered  as  constituting 
an  important  highway  for  the  migration  of  plants.  Stretching  over 
about  12°  latitude,  and  thus  including  within  its  extent  a  great  variety 
of  climate,  it  nevertheless  is  fairly  consistent  in  having  relatively 
good  water  relations  throughout. 

Rainfall  and  Temperature. 

Blanchtown  is  in  the  belt  of  winter  storms.  The  average  annual 
precipitation  is  10.77  inches.  But  at  Blanchtown,  as  at  other  semi- 
arid  stations,  there  is  not  a  little  variation  from  one  year  to  another 
in  the  amount  of  the  rainfall.  The  least  recorded  up  to  1912  was 
5.84  inches  and  the  greatest  was  19.71  inches.  Thus,  although  at 
times  the  rainfall  may  be  considerable,  it  is  nevertheless  always 
periodic,  so  that  there  is  a  marked  season  with  no  rains  of  moment, 
or  none  at  all,  during  which  the  perennial  plants  may  be  subject  to 
conditions  of  extreme  drought. 

There  are  apparently  no  temperature  records  available  for  Blanch- 
town. The  nearest  meteorological  station  is  Kapunda,  about  32 
miles  west.  The  altitude  of  the  latter  is  803  feet,  and  hence  the  tem- 
perature conditions  can  not  be  taken  as  being  parallel  to  those  at 
Blanchtown,  although  they  are  probably  similar.  However  this  may 
be,  the  temperature  for  Kapunda  may  serve  to  illustrate  certain  fea- 
tures of  the  climate  of  the  mallee  country  to  the  west  of  the  Murray, 
and  for  this  reason  they  are  summarized  in  table  15,  supplied  by  the 
Commonwealth  Bureau  of  Meteorology.  It  will  be  seen  that  the  mean 
maximum  temperature  at  Kapunda  is  71.1°  and  that  the  mean  mini- 
mum is  50°  F.  The  highest  temperature  at  the  station  recorded  up 
to  1912  was  113°  and  the  lowest  was  27°  F. 


110  PLANT   HABITS   AND   HABITATS   IN   THE 

Table  15.— Temperature  at  Kapunda,  South  Australia,  in  degrees  Fahrenheit. 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Mean  maximum 

85.9 
58.5 
72.2 
113 
41 
12 

4.4 

0 

85.7 
58.8 
72.3 
109 
41 
10.1 

3.2 

0 

79.2 
54.9 
67.0 
104 
40 
5.0 
0.4 
0 

70.5 

50.3 

60.4 

95 

35 

0.4 

0 

0.6 

63.3 

46.1 

54.7 

93 

30 

0 

0 

5.4 

57.2 

43.3 

50.2 

73 

27 

0 

0 

8.8 

55.7 

41.4 

48.6 

73 

29 

0 

0 
12.9 

59.0 

42.9 

50.9 

81 

30 

0 

0 

9.7 

64.0 

44.8 

54.4 

89 

29 

0 

0 

6.8 

71.0 

48.4 

59.6 

97 

33 

1.3 

0 

2.9 

78.8 

52.9 

65.5 

108 

38 

4.9 

0.6 

0.4 

83.4 
56.6 
70.0 
110 
39 
8.9 
2.7 
0 

Mean  minimum 

Mean  temperature   

Maximum  * 

Minimum  * 

Mean  No.  of  days  90°  or  over 
Mean  No.  days  100°  or  over. 
Mean  No.  nights  40°  or  under 

*  Fractious  of  a  degree  are  disregarded  in  maximum  and  minimum  temperatures. 

Vegetation. 

When  viewed  from  the  Central  Highlands  west  of  the  Murray  Flats 
the  landscape  has  much  of  the  monotony  as  well  as  color  of  the  sea. 
The  vegetation  is  bluish  green  and  extends  mile  on  mile  without  marked 
irregular  features,  except  an  occasional  rectangular  homestead,  to 
create  diversion  either  of  color  or  form.  Not  far  below  the  eastern 
horizon  a  faint,  lighter  line,  the  precipitous  farther  bank  of  the  Murray, 
cuts  the  view  and  reveals  where  the  river,  submerged  beneath  the 
general  level  of  the  plain,  makes  its  tortuous  course  to  the  sea.  Once 
entered,  the  woody  vegetation  of  the  Murray  Flats  retains  its  apparent 
monotony.  On  every  side  the  mallees  of  the  scrub  lift  their  rounded 
shoots  to  a  height  of  about  3  to  6  meters  (plate  32c).  Furthermore, 
there  is  little  apparent  difference  between  unlike  species,  and  there 
are  few  woody  plants  of  genera  other  than  Eucalyptus.  So  far  as  could 
be  determined  from  a  superficial  examination,  E.  oleosa  was  the  domi- 
nant species,  although  E.  odorata  was  found  in  large  numbers  also. 
The  latter  species  occurs  both  as  a  mallee  and  (at  the  western  edge 
of  the  miallee  scrub  proper)  as  a  small  tree.  Growing  in  the  scrub 
were  numbers  of  Dodoncea  bursarifolia  and  separated  groups  of  Mela- 
leuca parvifiora  (plate  32a).  The  individuals  of  the  mallee  scrub  are 
frequently  so  closely  placed  that  the  shoots  are  in  contact.  The 
mallees  cease  to  be  dominant  forms  as  the  river  gorge  is  approached, 
and  other  trees,  prominent  among  which  are  species  of  Casuarina, 
are  fairly  abundant.  Individual  specimens  of  mallees,  however, 
may  be  found  to  the  edge  of  the  goi^e. 

The  Murray  River  and  its  flood-plain  are  sunk  approximately  30 
meters  below  the  general  level  of  the  Murray  Flats.  When  seen  (No- 
vember 11,  1918)  the  river  was  still  running  high  and  was  about  200 
meters  from  bank  to  bank.  A  narrow  flood-plain  lay  on  one  or  both 
sides  of  the  stream,  and  on  these  there  are  open  forests  of  large  gums, 
Eucalyptus  rostrata,  and  a  few  specimens  of  introduced  Salix  sp. 
(plate  32b).  The  bases  of  many  of  the  trees  were  covered  with  water 
and  had  been  so  covered  for  several  months.  No  mallees  were  seen 
on  the  flood-plain. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  Ill 

At  various  places  on  the  Murray  Flats  west  of  Blanchtown,  farming 
operations  have  been  carried  on  for  several  years.  It  is  not  uncommon 
to  see  the  farm  fences  composed  of  the  "roots"  or  "stumps"  of  the 
mallees.  These  are  piled  loosely  into  long  and  low  walls.  I  was  in- 
terested to  note  that  there  were  no  especially  large  roots  in  the  fences. 
This  agreed  with  what  I  had  seen  in  excavations  by  the  roadside  in 
which  mallee  roots  had  been  in  part  exposed.  From  other  observa- 
tions also  it  appeared  that  the  stem  bases  of  the  mallees  of  the  region 
were  usually  not  large.  So  far  as  the  roots  of  the  mallee  of  the  region 
are  concerned,  it  seems  probable  that  they  are  largely,  but  not  exclu- 
sively, superficially  placed.  They  are  not  infrequently  exposed  in 
part  by  the  removal  of  the  soil  by  erosion,  and  under  such  circumstances 
the  stem  base  appears  as  a  flattened  crown  lying  close  to  the  level  of 
the  ground,  from  which  the  superficial  absorbing  roots  radiate  like 
spokes  in  a  wheel. 


MORPHOLOGICAL  ASPECTS  OF  THE  XEROPHYTIC  FLORA 
OF  SOUTH  AUSTRALIA. 

LEAF-SIZE  AND  LEAF-FORM. 

One  of  the  striking  features  of  the  vegetation  of  South  Australia 
is  the  xerophytic  stamp  that  characterizes  every  shrub  and  tree. 
This  impression  is  given  on  every  side — on  the  plains  about  Adelaide, 
in  the  Mount  Lofty  Ranges,  on  the  Murray  River  fiats,  on  the  rolling 
Central  Highlands,  about  Quorn  and  Mount  Remarkable,  as  well  as 
in  the  far  north  and  in  the  southwestern  districts.  Very  naturally 
the  xerophytic  characters  increase  with  an  increase  in  the  dryness  of 
the  habitat.  Where  the  rainfall  is  most  favorable  the  plants  on  the 
whole  are  relatively  large  as  well  as  abundant  and  the  leaves  they  bear 
are  not  only  numerous  but  relatively  large.  Thus  the  differences 
noted  are  those  of  degree  and  not  of  quality. 

The  range  in  the  modifications,  however,  may  be  extreme,  amounting, 
in  effect,  upon  the  contrast  of  the  extremes,  to  qualitative  differences. 
Thus  aphylly  is  occasionally  met  with  in  genera  with  leaf-bearing  or 
phyllodia-bearing  species.  A  condition  of  aphylly  connotes  the  ab- 
sence of  leaves  at  all  times  and  at  all  stages  of  development,  save 
possibly  in  seedlings.  There  are  apparently  no  perennials  with  de- 
ciduous habit  through  which  the  condition  of  aphylly  becomes  a  re- 
curring one.  On  the  contrary,  the  foliar  organs,  of  whatever  nature, 
can  be  said  to  be  constant,  used  in  a  restricted  sense,  and  thus 
are  exposed  fully  to  the  greatest  range  of  intensity  of  the  environmental 
conditions  where  the  species  occurs.  The  adjustments  to  the  environ- 
ment take  place  along  different  fines  and  naturally  affect  the  shoots 


112  PLANT   HABITS   AND   HABITATS   IN  THE 

in  a  great  variety  of  ways,  such  as  the  cuticularization  of  exposed 
surfaces,  the  formation  of  trichomes,  the  marked  formation  of  scleren- 
chyma,  the  development  of  resinous  or  other  secretions  which  cover 
the  shoots  at  least  in  part,  the  formation  of  water-storage  organs  or 
cells,  a  modification  in  the  direction  of  growth  in  some  manner  related 
to  light  and,  not  to  extend  the  list,  the  size  and  the  form  of  the  chloro- 
phyllous  organs  themselves.  The  precise  steps,  however,  by  which 
such  modifications  may  have  taken  place,  even  if  they  are  apparently 
related  directly  to  differences  in  the  water  relations,  for  example,  are 
necessarily  obscure  and  are  subjects  for  physiological  research. 

A  survey  of  the  leaf  characters  of  representative  perennials  of  South 
Australia  shows  a  strong  tendency  to  develop  leaves,  or  phyllodia, 
which  are  relatively  long.  This  is  most  marked  in  the  very  dry  regions. 
In  this  type  of  leaf  modification  there  is  a  reduction  in  the  amount  of 
chlorenchyma  of  whatever  kind,  and  the  leaves  may  be  reduced  to 
little  more  than  midribs  with  narrow  wings.  In  the  case  of  phyllodia, 
however,  the  leaf-stalks  on  which  they  are  based  may  become  very 
long,  which  apparently  is  also  a  secondary  development.  Under 
more  moist  conditions  of  growth,  however,  the  latter  undergo  a  ter- 
tiary modification  by  becoming  relatively  wide,  thus  increasing  the 
surface  to  a  marked  extent.  Such  reversion,  in  effect  if  not  in  fact, 
occurs  only  under  relatively  good  water  relations.  The  phyllodia  of 
Acacia  pycnantha,  the  ''golden  wattle,"  illustrate  the  feature  last 
referred  to.  The  transpiring  surface  is  also  increased  by  the  increase 
in  length  alone,  so  that  there  is  in  this  particular  an  apparent  conflict 
in  the  direction  of  development,  as  well  as  a  real  exception  to  the 
general  tendency  of  species  to  undergo  a  reduction  of  the  leaf-surface 
with  a  decrease  in  the  amount  of  available  water. 

These  features  can  be  illustrated  by  a  few  examples  of  leaf  or  phyllodia 
sizes.  Heterodendrum  oleasfoUum  is  a  small  tree  and  occurs  in  arid- 
semiarid  regions.  The  leaves  are  about  110  mm.  in  length  by  about 
14  mm.  in  width,  and  have  an  area,  one  side,  of  approximately  1,080 
sq.  mm.  The  ratio  of  length  to  width,  therefore,  is  nearly  8  to  1, 
while  the  ratio  of  area  to  length  is  approximately  19  to  1.  Acacia 
stenophylla  was  found  in  the  desert-arid  regions.  The  phyllodia  of  the 
species  may  become  of  great  length,  some  375  mm.  long;  they  measured 
5  mm.  in  width  and  had  a  surface,  one  side,  containing  about  1,700 
sq.  mm.  The  ratio  of  length  to  width  is  in  the  latter  instance  about 
75  to  1,  and  that  of  area  to  length  is  about  4.5  to  1.  In  this  connection 
it  can  be  remarked  that  in  simple  leaves,  circular  in  shape  and  thus 
with  the  greatest  possible  area,  the  ratio  of  length  to  breadth  is  unity 
and  that  of  area  to  length  varies  with  the  diameter  and  increases  in 
geometrical  ratio  directly  with  the  increase  in  diameter.  In  the 
case  of  leaf  sizes  about  equal  to  the  "microphylls"  of  Raunkiaer 
(Fuller,  1918),  2,025  sq.  mm.,  the  ratio  of  area  to  length  (diameter), 
in  circular  leaves  is  about  40  to  1. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


113 


A  "composite"  leaf  constructed  upon  the  average  length  and  width 
of  the  leaves  of  30  representative  species  growing  in  the  desert-semi- 
arid  regions  of  South  Australia  has  a  length  of  64  nun.  and  a  breadth 
of  5  mm.,  giving  the  length-breadth  ratio  nearly  13  to  1.  Mea'sure- 
ments  on  the  phyllodia  of  16  species  of  Acacia  give  an  average  length 
of  84  mm.  and  an  average  width  of  3.5  mm.,  or  a  ratio  of  length  to 
width  of  24  to  1.  The  average  leaf-area  was  not  determined  in  either 
class.  In  another  series  of  29  species  both  leaves  and  phyllodia  were 
measured  and  the  area  computed.  In  this  case  the  ratio  of  area  to 
length  was  4.7  to  1.  For  the  leaf  sizes  observed,  it  would  appear, 
therefore,  that  the  ratio  of  area  to  length  is  greatly  under  that  to  be 
expected  in  species  growing  under  moist  conditions — that  is,  in  species 
which  bear  leaves  with  equal  transpiring  surface,  or,  in  other  words, 
with  better  developed  lamina.  The  length-width  and  the  area-length 
ratios,  for  this  reason,  may  possibly  constitute  an  index  of  the  degree 
of  xerophylly  of  the  species.  Measurements  of  leaf  and  phyllodium 
sizes  are  given  in  table  16. 


Table  16. — Leaj  measurements,  desert-arid  -perennials  of  South  Australia. 

Species. 

Length. 

Width. 

Area. 

Species. 

Length. 

Width. 

Area. 

Acacia  aneura 

mm. 
57 
55 

100 
67 
20 
12 
88 
64 

140 
47 

110 
70 
85 
75 
31 

375 
34 
30 
85 
34 
26 
65 
32 
80 
46 
44 
28 

mm. 

8 

2.5 

1.6 

1 

8 

1 

5 

7 

1.5 

4 
26.6 

2 

1.6 

5 

3.5 

5 
10 

1 

3 

2 

4 

7 

1.6 

5 

5 

1.7 

2 

sq.  mm. 
350 
100 
140 

65 
140 

12 
350 
410 
210 
175 
1,050 
130 
120 
350 
100 
1,700 
300 

30 
200 

30 
110 
230 

32 
230 
190 

66 

60 

Eucalyptus  incrassata  var. 

dumo&a 

leucoxylon  var. 

macrocarpa  . . 
odorata 

mm. 

87 

90 
75 
86 
72 
47 
47 
135 
72 
210 
110 
96 

26 
20 
25 
9 
67 
90 
20 

mm. 

18 

25 
10 
18 

7 
10 

3.5 

1.5 

2 

6 
14 

5 

5 

1 
1 
1 
7 
6 
1 

sq.  mm. 
1,280 

1,400 
650 

1,000 
300 
290 
16C 
190 
140 

1,200 

1,080 
450 

95 
18 
22 
7 
450 
25 
18 

aneura  (narrow  form) 
brachystachya 

Fusanus  acuminatus 

Gravillea  stenobotrya 

Heterodendrum  oleisfolium . 

Leptospermum  isevigatum 

var  minus 
Melaleuca  glomerata 

uncinata 

parviflora 

Myoporum  platycarpum  . .  . 
Olearia  muelleri 

tetragonophylla 

Dodonsea  attenuata 

Eremophila  alternif olia 

brownii 

freelingii 

latrobei 

longifolia 

neglecta 

oppositifolia 

paisleyi 

Pholidia  scoparia 

114  PLANT   HABITS   AND   HABITATS   IN   THE 

FEATURES  OF  ROOTS  OF  SOUTH  AUSTRALIAN  PLANTS. 

Whatever  may  be  the  reasons,  there  appears  to  be  a  comparatively 
Umited  range  of  variation  in  the  types  of  roots  developed  in  perennial 
plants  of  South  Australia,  and  possibly  of  Australia  taken  as  a  whole; 
in  herbaceous  forms,  however,  such  does  not  appear  to  be  the  case. 
Thus  there  are  herbaceous  species  with  perennating  fleshy  roots  of 
various  types,  as  well  as  those  with  roots  that  are  fibrous,  and  the 
latter  may  be  various  as  to  form,  direction,  and  extent  of  their  de- 
velopment. As  to  the  perennials  of  the  state,  an  analogous  condition 
seems  not  to  exist.  The  roots  of  perennial  plants  may  be  divided,  as 
to  general  development,  into  those  which  may  be  said  to  be  specialized 
and  those  which  are  generahzed.  The  former  are  either  obligately 
deeply  penetrating  or  they  are  obligately  shallowly  placed.  In  certain 
regions,  as  for  example  in  southern  Arizona,  all  three  root-types  are 
to  be  found.  To  mention  only  one  root-type,  the  obligate  shallow  form, 
it  may  be  said  that  this  is  associated  in  Arizona  almost  exclusively 
with  the  quality  of  fleshiness  in  the  species.  In  South  Australia,  on 
the  other  hand,  roots  of  this  character  appear  to  be  quite  wanting,  or 
at  least  they  remain  to  be  demonstrated.  Possibly  this  is  because  of 
the  lack  of  fleshy  perennials  of  a  type  analogous  to  the  American  cacti. 
It  therefore  appears  to  be  necessary  to  account  for  the  absence  of  per- 
ennials with  water-storage  capacity  in  South  Australia  in  order  to 
account  for  the  failure  to  develop  obhgately  shallow  roots.  Both  of 
these  are  certainly  not  without  their  difiiculties. 

It  would  appear  to  be  puzzUng  that  herbaceous  species  with  peren- 
nating subterranean  parts  are  developed  in  large  numbers  in  a  region 
in  which  fleshy  perennials  do  not  occur.  It  does  not  seem  improbable 
that  certain  of  the  environmental  conditions  favorable  to  the  growth 
of  the  one  may  also  be  favorable  to  that  of  the  other.  Thus,  the  roots 
of  certain  cacti,  as  mentioned  in  another  place,  require  a  well-aerated 
soil  as  well  as  one  that  is  suitably  moist  and  of  a  fairly  high  tempera- 
ture. In  all  cases  moisture  is  a  condition  sine  qua  non  of  root-growth. 
The  optimum  temperature  for  growth  may  vary  as  between  different 
fleshy  perennials,  but  it  remains  to  be  shown  that  the  same  is  true  as 
to  the  oxygen-supply.  That,  as  a  matter  of  fact,  such  fleshy  plants 
as  various  species  of  the  cacti  can  live  in  parts  of  Australia,  including 
South  Australia,  is  well  known.  So  far  as  is  known,  also,  these  intro- 
duced forms  develop  roots  of  a  type  characteristic  of  them  in  other 
lands.  In  short,  it  can  be  said  that  the  type  of  roots  which  develop 
in  the  upper  soil  layers,  and  which  do  not  normally  attain  to  any  con- 
siderable depth  in  the  soil,  is  quite  wanting  in  South  Australia,  for 
reasons  which  are  not  apparent. 

It  is  probable  that  a  close  study  of  the  roots  of  the  perennials  would 
show  many  with  a  well-developed  tap-root  and  with  an  obligate, 
deeply  penetrating  habit  of  growth.    As  a  matter  of  fact,  I  saw  but 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  115 

few  that  appeared  to  be  such  and  none  that  I  was  quite  sure  of.  There 
are  many  species  with  what  may  be  called  an  intermediate  condition. 
Such  would  be  Kochia  sp.,  Pholidia  scopana,  and  Eremophila  free- 
lingii  at  Copley,  and  several  species  of  Eucalyptus  of  different  habit 
of  growth  and  at  different  places.  At  Quom,  however,  Acacia  calami- 
folia  seems  to  have  a  root-system  in  which  the  tap-root  is  very  well 
developed  and  in  which  the  laterals  do  not  appear  to  exist  near  the 
surface  of  the  ground.  To  surely  determine  the  point  would  require 
more  observations  on  the  habits  of  the  species  than  I  was  able  to 
make. 

Without  doubt  the  most  usual  type  of  root-system  in  the  perennials 
of  South  Australia  is  the  generalized  form,  or  that  type  in  which  the 
roots  are  plastic,  so  that  under  one  set  of  conditions  they  may  pene- 
trate deeply,  under  another  they  may  He  close  to  the  surface  of  the 
ground,  or  finally  under  a  third  they  may  both  penetrate  deeply  as 
well  as  extend  widely  in  one  and  the  same  specimen.  As  will  be 
gathered  from  what  has  been  remarked  in  the  preceding  paragraphs  on 
speciaUzed  roots,  practically  all  of  the  perennials  whose  roots  were 
observed  have  the  generalized  root-habit.  For  obvious  reasons, 
however,  only  the  more  superficially  placed  of  the  roots  of  such  plants 
can  usually  be  studied,  but  in  certain  instances  the  development  of 
such  superficial  roots  is  very  marked.  For  example,  at  Warren's 
Gorge,  near  Quorn,  the  superficial  roots  of  Eucalyptus  leucoxylon  var. 
pauperita,  which  lie  about  20  cm.  deep,  were  traced  16  meters  away 
from  the  base  of  the  tree.  Marked  development  of  superficial  roots 
was  seen  in  other  species  of  Eucalyptus,  including  mallees,  in  several 
locahties;  no  very  deeply  placed  roots  of  species  of  the  genus  were 
actually  observed.  By  a  wash  near  Quorn  a  penetration  of  2  meters 
was  noted  and  the  root  gave  every  appearance  of  sinking  deeper  than 
this.  Reports,  however,  were  not  wanting  to  the  effect  that  roots  of 
Eucalyptus  might  attain  to  very  considerable  depths  and  in  fact  were 
not  infrequently  met  in  digging  operations.  I  was  unable  to  verify 
such  reports,  but  from  what  I  saw  of  the  roots  of  Eucalyptus  I  would 
suppose  deep  root  penetration  to  be  possible  under  appropriate  con- 
ditions. 

An  interesting  feature  of  species  having  generalized  roots  is  the 
frequency  with  which  they  reproduce  vegetatively.  This  occurs 
through  the  springing  of  shoots  from  the  horizontally  placed  roots. 
Although  the  vegetative  reproduction  was  not  studied  especially,  it 
was  noted  at  Quorn  mCasuarina  sp.,  Hakea  leucoptera,  and  Templetonia 
egena,  and  observed  at  other  places  and  in  other  species. 

Especial  study  of  the  roots  of  the  perennials  of  the  state  will  prob- 
ably show  many  interesting  forms  of  specialization  and  adjustments 
to  the  physical  environment  which  may  be  of  moment  in  the  survival 
of  the  species.    It  does  not  seem  improbable,  for  example,  that  roots 


116  PLANT   HABITS   AND   HABITATS   IN   THE 

of  a  semi-fleshy  type  may  be  found  in  species  of  Xanthorrhoea,  as  is  the 
case  in  analogous  forms  elsewhere.  The  high  water-retaining  capacity 
of  the  roots  of  certain  woody  species,  as  Gravillea  stenobotrya  and 
other  forms,  is  probably  of  great  importance  in  the  water-economy  of 
such  plants.  But  the  most  striking  of  these  must  be  considered  to 
be  species  of  Eucalyptus  which  assume  the  mallee  habit.  In  them  the 
short  stem  and  the  enlarged  root-crown  together  constitute  a  very 
remarkable  water-storage  organ  which  would  seem  to  be  capable  of 
holding  sufficient  water  to  carry  the  shoot  over  long  periods  of  drought. 
In  such  a  bulbous  organ  it  would  be  expected  that  the  "  feeding  " 
roots  would  be  so  situated  that  the  utmost  advantage  would  be  taken 
of  the  rainfall.  This  would  mean  the  placing  of  the  roots  at  such  a 
depth  as  would  insure  the  absorption  of  water  very  soon  after  the  com- 
mencement of  rains  as  well  as  the  continuation  of  absorption  of  water 
for  a  relatively  long  period  after  the  rains  were  over.  It  is  possible 
that  a  further  study  of  the  roots  of  the  mallees  would  show  such  root- 
development,  and  in  the  species  having  the  mallee  habit  there  is  a 
tendency  looking  to  specialization  in  relatively  shallow  roots,  even  if 
under  favorable  conditions  a  considerable  root-depth  may  be  attained. 
A  study  of  species  with  a  facultative  mallee  habit  would  be  of  interest 
in  this  connection. 

The  depth  at  which  the  superficial  roots  of  perennials  are  placed  is 
variable,  but  in  no  case  observed  was  it  seen  to  be  as  shallow  as  those 
of  certain  cacti  in  southern  Arizona,  for  example.  At  Oodnadatta 
the  horizontal  roots  of  Eucalyptus  rostrata  lie  at  a  depth  of  about 
60  cm.  beneath  the  surface,  but  these  may  not  be  the  most  shallowly 
placed  roots  of  the  species.  Acacia  linophylla  of  the  sandhills  east  of 
that  place  has  superficial  roots  which  run  within  a  very  few  centimeters 
of  the  surface,  although  the  exact  depth  was  not  determined.  At 
Copley  the  most  superficial  laterals  of  specimens  of  Pholidia  scoparia, 
growing  by  a  wash,  were  seen  to  lie  at  a  depth  of  40  cm.,  and  the  super- 
ficial roots  of  Kochia  sp.,  in  a  similar  situation,  were  ascertained  to  lie 
within  about  10  cm.  of  the  surface.  At  Quorn  the  superficial  roots 
of  Eucalyptus  leucoxylon  var.  pauperita  were  found  to  be  20  cm. 
deep. 

At  Copley  some  measurements  were  made  on  the  greatest  pene- 
tration of  the  roots  of  annuals  to  be  found  at  the  time  of  my  visit, 
July- August,  showing  that  for  the  most  part  they  lie  within  10  cm.  of 
the  surface  of  the  ground.  The  extreme  depth  observed  was  in  the 
case  of  a  specimen  of  Zygophyllum  crenatum  growing  on  a  slope  below 
high  and  rocky  hills,  where  the  soil  was  relatively  coarse.  Here  in 
one  specimen  a  penetration  of  13.5  cm.  was  found,  although  in  two 
others  of  the  same  species  the  extreme  depth  attained  was  8  and  8.5 
cm.,  respectively. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  117 

NOTES  ON  SOME  STRUCTURAL  FEATURES  OF  PERENNIALS. 

Although  the  material  at  hand  was  not  primal  ily  collected  or  pre- 
pared for  anatomical  study,  it  was  found  that  by  proper  handling  and 
treatment  it  yielded  much  better  results  from  this  point  of  view  than 
was  at  first  expected,  probably  because  so  large  a  proportion  of  the 
tissues  of  the  leaves  or  phyllodia  is  composed  of  mechanical  tissue 
of  whatever  sort.  The  following  sketch  of  some  of  the  most  striking 
features  of  the  anatomy  of  the  chlorophyll-bearing  organs  of  represent- 
ative perennials  is  based,  so  far  as  the  original  observations  are  con- 
cerned, wholly  on  the  study  of  such  herbarium  material. 

In  this  brief  survey  of  the  anatomy  of  the  species  the  observations 
have  been  almost  wholly  confined  to  such  tissues  as  are  most  directly 
concerned  with  the  water  relations  of  the  plants.  Scant  reference 
has  been  accorded  any  other  features.  No  attempts,  therefore,  have 
been  made  looking  to  thorough  or  exhaustive  treatment,  much  as 
that  is  desirable,  inasmuch  as  the  subject  of  structure  should  and  un- 
doubtedly will  receive  adequate  attention  from  others  who  will  study 
living  material,  which  was  not  practicable  in  the  present  instance. 
Observations  were  made  on  the  following  species: 

Acacia  aneura.  Eremophila  alternifolia.  Pholidia  scoparia. 

continua.  brownii.  Fusanus  acuminatus. 

linophylla.  latrobei.  Gravillea  stenobotrya. 

tarculiensis.  longifolia.  Hakea  leucoptera. 

tetragonophylla.  neglecta.  multilineata. 

Bossisea  walkeri.  oppositi folia.  Melaleuca  parviflora. 

Casuarina  stricta.  paisleyi.  Pittosporum  phillyrseoides. 

Dodonaja  attenuata.  rotundifolia.  Triodia  irritans. 
lobulata. 

THE  PHYLLODIA  IN  SOME  SPECIES  OF  ACACIA. 
All  species  of  Acacia  which  were  studied  in  the  field  either  bear 
phyllodia  in  the  place  of  leaves  or  are  aphyllous.  Such  organs  show 
most  clearly  the  impress  of  the  subaerial  environment.  Naturally 
the  response  takes  place  along  a  variety  of  lines,  but  in  a  region  of 
great  aridity  it  has  much  to  do  with  the  water  relation.  This  is  re- 
vealed in  devices  of  various  kinds  which  lead  to  a  conservation  of 
water,  but  it  is  also  shown  in  the  relatively  great  formation  of  cell- 
walls,  a  direct  result,  as  already  pointed  out,  of  a  small  water-supply. 
All  of  these  features  are  shown  well  in  various  species  of  the  genus 
Acacia,  the  leading  characteristics  of  the  structure  of  which  are  known. 
I  shall  point  out,  in  the  present  paper,  some  of  the  most  striking 
features  in  the  structure  of  a  few  species  which  were  found  in  the 
desertic-arid  portions  of  South  Australia  and  certain  of  which  may 
not  be  generally  known.  Of  the  species  A.  aneura,  continua,  lino- 
phylla, tarculiensis,  and  tetragonophylla,  all  except  A.  continua  and  A. 
tarculiensis  were  found  at  Oodnadatta;  A.  continua  was  studied  at 
Quorn,  and  A.  tarculiensis  was  seen  at  Tarcoola,  its  type  habitat. 


118  PLANT   HABITS   AND   HABITATS   IN   THE 

A.    ANEURA   AND   A.    LINOPHYLLA. 

The  phyllodia  of  these  species  are  long,  in  the  latter  species  linear, 
although  in  one  form  those  of  A.  aneura  are  rather  broad.  Only  the 
narrow  form  in  this  species  was  examined.  The  structure  of  the 
phyllodia  in  the  two  species  is  so  much  alike  that  a  characterization 
of  that  of  one  only,  A.  linophylla,  will  be  sufficient.  As  figure  12 
indicates,  in  cross-section  the  phyllode  is  oval  with  crenulate  margin. 
Opposite  the  elevations  of  the  latter  is  sclerenchyma  which  extends 
to  the  epidermis,  and  opposite  the  hollows  are  masses  of  chlorenchyma. 
The  alternation  of  the  two  tissues  gives  rise  to  the  striations  charac- 
teristic of  the  phyllodia.  The  sclerenchyma  masses  reach  to  the  con- 
ductive tissue,  of  whatever  size  or  relative  importance.  There  is  also 
mechanical  tissue  on  the  inner  sides  of  each  of  the  fibro-vascular  bun- 
dles. Longitudinal  sections  of  the  phyllodia  show  that  the  latter  tissue 
is  only  in  part  fibrous,  but  that  the  portion  placed  near  the  epidermis 
is  of  short  cells,  cuboid  in  fact — that  is,  hjrpoderm.  There  is  a  rela- 
tively large  amount  of  mechanical  tissue.  The  chlorenchyma  is  com- 
posed of  isolated  strands,  masses  in  section,  of  palisade  cells  which 
(as  figure  14  indicates)  are  relatively  narrow  and  long.  On  the  inner 
side  they  abut  on  cuboid  cells  only,  which  separate  them  from  the 
tracheae  of  the  conductive  system.  On  the  peripheral  side  they  touch 
the  inner  wall  of  the  epidermis  where  the  latter  is  sharply  infolded  to 
form  the  furrows  previously  mentioned.  The  epidermis  has  relatively 
thin  vertical  and  inner  walls,  and  the  external  wall  varies  in  thickness, 
being  heavy  on  the  ridges  and  relatively  light  in  the  furrows.  It  is 
in  the  latter  only  that  stomata  are  to  be  found  where  they  are  situated 
on  the  inner  portion  of  the  sides  as  well  as  at  the  bottom.  The  stomata 
do  not  appear  to  have  especial  protective  devices  of  and  by  them- 

EXPLANATIONS   OF  FIGURES   12   TO   21. 

FiQ.  12.  Acacia  linophylla,  transverse  eection  of  phyllode,  semi-diagrammatic,  X72.  The  large 
proportion  of  mechanical  tissue  is  indicated  (sc)  and  the  protected  position  of  the 
chlorenchyma  (ch).     The  relatively  heavy  covering  of  hairs  is  indicated  by  stippling. 

Fig.  13.  Same.  Detail  of  margin  of  phyllode  to  show  the  nature  of  the  sclerenchma  and  epider- 
mal cells  and  the  presence  of  glandular  trichomes,  X700. 

Fio.  14.  Same.  Detail  of  inner  portion  of  chlorenchyma  showing  its  relation  to  the  fibro- 
vascular  bundle  at  the  left,  X700. 

Fig.  15.  Acacia  continua,  transverse  section  of  chlorophyll-bearing  stem,  X52.5. 

Fig.  16.  Acadia  tetragonophylla,  cross-section  of  phyllode,  semi-diagrammatic,  X85. 

Fig.  17.  Caauarina  stricta,  transverse  section,  semi-diagrammatic,  of  chlorophyll-bearing  stem, 
X  72.  The  chlorenchyma  is  shown  partly  protected  by  the  heavy  epidermis  and 
partly  by  the  furrows  with  the  trichomes,  of  which  the  latter  are  not  shown.  The 
enlarged  outer  ends  of  the  sclerenchyma  also  act  in  the  same  capacity. 

Fig.  18.  Eremophila  alternifolia,  detail  of  young  stem  with  glandular  trichome,  X525. 

Fig.  19.  Same.  Trancverse  section  of  leaf  showing  old  glandular  trichome,  heavy  epidermia, 
and  its  covering  of  a  resinous  substance. 

Fig.  20.  Eremophila  freelingii,  semi-diagrammatic  transverse  section  of  leaf  to  show  the  size  and 
frequency  of  internal  glands  (gZ),  X52.5. 

Fig.  21.  Eremophila  rotundifolia,  longitudinal  section,  semi-diagrammatic,   X52.5,  to  show  the 
relatively  large  internal  glands  and  the  very  heavy  covering  of  hairs  (<r). 
In  the  figures  the  tissues  are  designated  as  follows:  ch,  chlorenchyma;  fv,  conductive  tiaaue; 

Oly  internal  gland;  hd,  hypoderm;  «c,  sclerenchyma. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA. 


119 


Figures  12  to  21. 


120  PLANT   HABITS   AND   HABITATS   IN   THE 

selves,  but  their  position,  as  well  as  the  presence  of  trichomes,  ap- 
parently suffices  in  this  regard.  The  outer  surface  of  the  epidermal 
cells  is  sharply  arched  and  trichomes  of  characteristic  sorts,  both 
glandular  and  protective,  spring  between  these  cells;  the  former  have 
relatively  widely  expanded  heads  which  collapse  in  age,  and  the  latter 
are  apparently  only  short,  two-armed,  giving  an  appearance  much  like  a 
section  of  shield  hairs.  The  glandular  hairs  are  especially  abundant. 
Acacia  continua. 

According  to  Tate,  Acacia  continua  is  one  of  three  species  of  the 
genus  in  South  Australia  which  has  neither  leaves  nor  phyllodia.  It  is 
a  shrub  with  short  branches,  2.5  to  5  cm.  in  length,  which  resemble 
spines.  The  species  was  observed  at  Quorn,  where  it  occurs  under 
fairly  good  conditions,  so  far  as  moisture  is  concerned. 

A  cross-section  of  one  of  the  short  branches  is  somewhat  angular 
in  outline  (fig.  15).  The  general  arrangement  of  the  tissues  is  ap- 
parently about  as  in  cylindrical  phyllodia  of  other  species.  That  is, 
there  is  a  large  central  portion  composed  of  chlorophyll-free  paren- 
chyma, a  peripheral  band  of  chlorenchyma,  masses  of  sclerenchyma 
extending  in  from  the  angles,  and  an  epidermis  with  a  well-developed 
cuticle.  Trichomes  appear  to  be  wholly  wanting,  and  no  secretion  of 
any  kind  was  seen  to  cover  the  epidermis.  A  leading  departure  from 
the  usual  condition  to  be  found  in  phyllodia  (which  appears  to  be  a 
quantitative  variation,  however)  is  in  the  development  of  tissue  with 
especially  heavy  walls,  either  fibrous  or  otherwise.  The  hypoderm  of 
the  material  studied  was  little  developed,  although  it  was  regularly 
present ;  also,  there  is  relatively  little  of  the  fibrous  tissue  between  it 
and  the  more  deeply  placed  fibro vascular  systems.    Finally,  the  cell- 

EXPLANATIONS   OF   FIGURES   22   TO   31. 

Fia.  22.  Fusanus  acuminatus,  fragment  of  leaf  showing  chlorenchyma  and  a  group  of  tracheida, 
X350. 

Fig.  23.  Same.  Cross-section  of  leaf  to  show  the  heavy  epidermis  consisting  ot  two  layers  of 
cells,   X350. 

Fig.  24.  Gravillea  stenobotrya,  semi-diagrammatic  transverse  section  of  leaf.  The  various  tissues 
are  as  indicated.     Trichomes  and  stomata  are  confined  to  the  ventral  side.     X52.5. 

Fig.  25.  Same.  Detail  of  leaf,  dorsal  side,  in  cross-section  to  show  the  greatly  elongated  epi- 
dermal cells  and  well-marked  palisades,  X350. 

Fig.  26.  Hakea  leticoptera,  leaf  fragment,  in  transverse  section,  with  very  heavy  epidermis  and 
deeply  sunken  stoma  and  papillate  processes  in  stomatal  canal.  The  presence  of 
sclerenchymatous  fibers  in  the  palisade  chlorenchyma  is  shown.      X350. 

Fig.  27.  Hakea  multilineata,  semi-diagrammatic  cross-section  of  leaf.  The  prominent  devel- 
opment of  mechanical  tissue  and  dorsiventral  nature  of  the  leaf  structure  are 
indicated.     X52.5. 

Fig.  28.  Same.  Fragment  of  leaf,  cross-section,  to  show  heavy  epidermis,  deeply  sunken  stoma, 
and  pronounced  palisade  character  of  the  chlorenchyma,  X350. 

Fig.  29.  Pittosporum  phillyrcEoides,  fragment  of  dorsal  side  of  leaf,  transverse  section,  to  show 
the  2-  or  3-layered  epidermis,  X350. 

Fig.  30.  Same,  ventral  side  of  leaf.  The  heavy  outer  epidermal  wall,  the  single  cell  layer  of  the 
epidermis,  and  the  superficially  placed  stoma  are  indicated.     X350. 

Fig.  31.  Triodia  irritans,  transverse  section  of   leaf,  semi-diagrammatic,  showing  its   infolded 
condition  and  the  position  and  relative  abundance  of  the  main  tissues,  X85. 
The  tissues  are  designated  as  follows:  ch,  chlorenchyma;  ep,  epidermia ; /»,  fibro- vascular  tissue; 

»e,  sclerenchyma. 


ARID    PORTIONS   OF    SOUTH    AUSTRALIA. 


121 


30 

Figures  22  to  31. 


122  PLANT   HABITS   AND   HABITATS   IN   THE 

walls  of  the  innermost  central  parenchyma  are  thin.  The  material 
examined  appeared  to  be  mature,  and  if  so,  the  lack  of  sclerenchyma  in 
quantity  is  a  noteworthy  feature  of  the  structure  of  the  species. 

Acacia  tarculiensis. 

Acacia  tarculiensis  is  a  shrub  of  compact  habit  of  growth.  The 
phyllodia  are  broad  and  numerous,  so  that  the  transpiring  surface  is 
very  considerable.  This  is  in  marked  contrast  to  A.  aneura  and  A. 
linophylla,  as  will  be  perceived. 

The  phyllodia  of  A.  tarculiensis  are  of  a  steel-blue  color  and  the 
margins  have  a  distinct  line  of  dark  brown.  In  transverse  section  the 
following  are  the  most  striking  structuial  features:  Chlorenchyma 
and  sclerenchyma  alternate  beneath  the  epidermis,  the  formei  lying 
mainly  but  not  wholly  in  the  shallow  hollows  of  the  wavy  margin  of 
the  section.  The  bands  of  supporting  tissue  are  narrow  and  the 
cell-walls  are  not  so  well  developed  as  in  the  two  species  above  referred 
to.  The  outer  epidermal  wall  is  fairly  heavy.  The  guard  cells  of  the 
stomata  are  deeply  placed  and  thus  are  at  the  bottom  of  short  tubes 
composed  largely  of  the  thickened  outer  walls.  The  chlorenchyma  is- 
composed  of  two  rows  of  rather  narrow  cells  which  abut  on  chloro- 
phyll-free parenchyma,  which  in  turn  is  situated  next  to  the  conductive 
elements.  The  latter  lie  at  about  the  same  distance  beneath  the  surface 
of  the  phyllode  and  thus  inclose  the  greatest  single  portion  of  the 
tissues,  namely,  the  chlorophyll-free  interior  parenchyma,  which  is 
made  up  of  relatively  large  cells. 

Trichomes  of  whatever  sort  do  not  appear  to  be  a  feature  of  the 
phyllodia  "blades"  or  lamina.  On  the  "blades"  of  the  older  phyllodia 
only  very  widely  scatteiing  remains  of  trichomes  are  to  be  found. 
These  appear  to  be  of  two  kinds  only,  namely,  a  short-stalked  and 
small  secreting  hair  and  a  larger  and  two-armed  covering  hair.  The 
material  did  not  show  the  hairs  to  advantage,  but  suggested  that  they 
are  not  plentiful.  The  most  striking  trichomes  of  the  phyllodia, 
however,  are  to  be  found  only  along  the  margins  and  are  composed 
of  chains  of  cells,  the  terminal  one  being  the  largest,  all  of  which, 
in  the  herbarium  material  studied,  are  dark  brown  in  color  and  appear 
to  be  secretory.  The  outer  edge  of  the  blade  of  the  phyllode  is  covered 
heavily  with  a  nearly  colorless  material,  the  nature  of  which  I  did  not 
attempt  to  learn,  but  it  gave  evidence  of  having  originated  in  the  hairs. 
It  is  probable,  therefore,  that  the  trichomes  are  glandular.  The  origin 
of  the  hairs  was  not  determined.  The  tissues  immediately  beneath 
these  hairs,  to  a  depth  of  3  to  4  cells,  is  discolored  in  a  fashion  analogous 
to  that  of  the  hairs  themselves.  The  cells  are  otherwise  colorless, 
small,  and  have  a  curious  appearance  of  being  in  the  process  of  division 
on  a  plane  parallel  to  the  leaf  margin.  A  noteworthy  strand  of  con- 
ductive tissue  underlies  the  marginal  tissue  just  referred  to. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  123 

Acacia  tetragonophylla. 

In  Acacia  tetragonophylla  the  phyllodia  are  needle-shaped  and  short. 
Moreover,  in  especially  dry  habitats  or  during  dry  seasons  they  may 
be  largely  shed,  thus  reducing  the  transpiring  surface.  An  analogous 
condition  was  observed  in  A.  colletioides,  having  similar  phyllodia, 
at  Ooldea.  On  the  other  hand,  where  the  environment  is  relatively 
moist,  as  in  certain  habitats  at  Copley,  the  phyllodia  appear  to  remain 
for  several  years. 

The  leading  features  of  the  structure  of  the  phyllodia  of  the  species 
(fig.  16)  include  prominent  masses  of  sclerenchyma,  a  part  of  which 
project  outward  from  the  conductive  tissue  to  the  epidermis,  and  a 
part  between  it  and  the  central  parenchyma,  the  central  non-chloro- 
phyllous  parenchyma,  and  the  masses  of  chlorenchyma  which  lie 
exterior  to  the  latter  and  between  the  peripherally  placed  scleren- 
chyma. The  cuticle  is  fairly  heavy.  No  trichomes  or  resinous  secre- 
tion were  observed.  Thus  there  appears  to  be  a  striking  absence  of 
certain  features  clearly  related  to  the  extremely  arid  environment  in 
which  the  species  occurs.  However,  the  fact  that  the  phyllodia  are 
of  small  size  and  fall  away  readily  may  be  a  reasonable  explanation 
of  this  condition.  The  relatively  large  proportion  of  cells  with  heavy 
walls  is,  as  has  already  been  referred  to,  a  direct  expression  of  imme- 
diate effects  of  an  arid  environment  and  is  not  related  directly  to  the 
storage  or  to  the  husbanding  of  the  water-supply. 


124         PLANT  HABITS  AND  HABITATS  IN  THE 

NOTES  ON  CERTAIN  OTHER  SPECIES  OF  THE  REGION. 

BoSSIiEA  WALKERI. 

This  is  a  low  shrub  of  rather  loose  habit  of  growth  and  leafless. 
The  branches  are  flattened,  almost  winged.  The  species  was  observed 
in  the  neighborhood  of  Ooldea,  where  it  occurs  mainly  on  dry,  sandy 
ridges.*  A  cross-section  of  a  stem  shows  the  peripherally  placed 
chlorenchyma,  which  is  fairly  distinctly  grouped  and  made  up  of  a  short 
form  of  pahsade  cells,  three  layers  or  so  in  thickness,  and,  within  the 
chlorenchyma,  the  central  portion  of  the  stem  of  which  is  largely 
composed  of  parenchyma,  much  of  which  was  seen  to  contain  starch- 
like granules.  A  leading  feature  of  all  the  parenchymatous  tissue  is 
the  relatively  heavy  walls,  which  are  pitted.  Sclerenchyma  occurs 
in  connection  with  the  conductive  tissue  and  is  most  abundant  at  the 
central  portion  of  the  stem,  although  large  and  conspicuous  masses 
are  to  be  found  not  far  beneath  the  stem  margins.  The  epidermis  is 
made  up  of  relatively  deep  cells,  with  a  heavy  cuticle,  and  is  underlaid 
by  a  subepidermal  tissue,  very  regular  in  appearance,  and  composed 
of  rectangular  cells  placed  at  right  angles  to  the  stem  surface  and  which 
may  or  may  not  contain  chlorophyll.  A  cross-section  of  the  stem  shows 
that  the  surface  is  not  plane  but  ridged.  The  stomata  appear  to  be 
confined  to  the  bottom  of  the  furrows  between  the  latter.  They  are 
situated  somewhat  below  the  general  surface  of  the  stem,  therefore, 
and  the  guard  cells  are  protected  by  a  fairly  heavy  cuticular  develop- 
ment. No  trichomes  of  any  kind  were  found  on  the  material  studied. 
Casuarina  stricta. 

The  equisetum-like  branches  of  Casuarina  stricta^  which  carry  on 
the  leaf  function,  have  an  intricate  structure  which  appears  to  cor- 
respond in  the  essential  points  to  that  of  C.  equisetifoUa  as  described 
by  Solereder  (1899 :  885) .  Only  certain  features,  clearly  associated  with 
the  xerophytic  habit  of  the  species,  need  for  that  reason  be  referred  to 
in  this  place.  The  structural  arrangement  is  intimately  associated 
with  the  presence  of  longitudinal  grooves  and  ridges  characteristic 
of  the  "internodes"  (fig.  17).  The  chlorenchyma,  pahsade  tissue,  is 
confined  to  the  sides  of  the  grooves,  and  in  cross-section  of  the  stem 
it  appears  as  separate  masses.  Between  the  chlorenchma,  and  between 
it  and  the  periphery  of  the  stem,  there  is  only  or  mainly  sclerenchyma. 
Stomata  are  confined  to  the  sides  and  bottoms  of  the  grooves.  Tri- 
chomes are  present  in  the  grooves,  from  the  bottom  of  which  they  take 
their  origin.  The  inner  portion  of  the  chlorenchyma  is  only  sUghtly 
more  deeply  placed  than  the  bottom  of  the  grooves.  A  distinct  cell- 
layer,  endodermis,  bounds  the  inner  face  of  the  chlorenchyma. 

Cortical  conductive  tissue  Ues  opposite  the  ridges  and  hence  some- 
what deeper  than  the  chlorophyll-bearing  tissue,  but  on  a  line  sepa- 

*Spe  page  88  and  plate  29a. 


ARID    PORTIONS    OF   SOUTH   AUSTRALIA.  125 

rating  that  of  each  ridge.  On  either  side  of  the  last,  and  joining  it  with 
the  endodermis,  are  water-storing  tracheids,  which,  however,  are  not 
especially  well  developed  in  the  material  of  C.  stricta  studied.  Within 
the  latter  there  extends  around  the  periphery  of  the  central  cylinder 
a  ring  of  sclerenchyma  which  appears  to  be  of  a  twofold  nature,  the 
inner  portion  at  least  being  fibrous,  but  this  does  not  appear 
throughout  the  entire  "internode."  Usually  within  the  zone  of  the 
cortical  conductive  tissue  is  found  that  of  the  central  cylinder,  the 
separate  fibro-vascular  bundles  of  which  alternate  with  the  ridges 
and  hence  are  opposite  the  furrows  above  referred  to,  and  alternate 
with  the  cortical  conductive  tissue.  Some  sclerenchyma  appears  with 
the  separate  bundles  of  conductive  tissue  in  the  central  cylinder. 
A  fairly  thick-walled  parenchyma  constitutes  the  ground  tissue  of 
the  stem. 

The  leading  points  of  interest  in  connection  with  the  structure  of 
the  stem,  from  the  present  point  of  view,  can  be  said  to  be  very  perfect 
protection  against  rapid  water-loss  afforded  by  the  outer  cortex  with 
its  heavy  development  of  sclerenchyma,  the  fairly  deep  and  narrow 
furrows  with  protective  trichomes,  the  presence  of  stomata  in  the 
furrows  only,  and  the  close  association  of  chlorenchyma  and  the  water- 
conductive  and  water-storing  tissue  of  the  cortex.  These  morpho- 
logical features,  taken  in  connection  with  the  great  reduction  in  the 
exposed  surface,  point  to  very  perfect  adjustment  to  an  environment 
in  which  a  rather  poor  water-supply  is  associated  with  an  atmosphere 
which  has  a  low  moisture-content  much  of  the  year. 

DoDONiEA   ATTENUATA   AND   D.    LOBULATA. 

The  leaves  of  Dodoncea  attenuata  have  distinct  dorsal  and  ventral 
sides.  They  are  of  fair  size  and  do  not  have  so  marked  a  xerophytic 
appearance  as  most  of  the  other  species  of  perennials  examined.  This 
characteristic  is  carried  out  in  the  structure  as  well.  A  cross-section 
of  the  leaves  shows  a  bifacial  arrangement  of  the  chlorenchyma. 
That  on  the  dorsal  side  is  distinctly  palisade  and  that  on  the  ventral 
side  is  well-marked  spongy  parenchyma.  Stomata  are  on  the  ventral  sur- 
face only  where  they  either  he  on  a  level  with  the  leaf-surface  or  in  some 
instances  they  were  seen  to  project  slightly  above  it.  The  epidermis 
is  not  heavy.  The  outer  walls  arch  outward  somewhat.  Sclerenchyma 
is  to  be  found  in  association  with  the  large  conductive  tissue  which 
constitutes  the  "midrib"  of  the  leaf,  and  in  no  other  place.  Short- 
stalked,  multicellular,  shield-shaped  trichomes  are  sparingly  present 
on  both  leaf-surfaces.  The  trichomes  have  the  appearance  of  being 
glandular,  yet  no  resinous  or  other  substance  was  found  on  the  leaf- 
surface  contiguous  to  them  in  the  material  examined;  but  in  young 
leaves  the  surface  is  highly  polished,  as  if  lacquered,  and  it  is  probable 
that  the  substance  is  a  secretion  derived  from  such  trichomes. 

The  structure  and  the  more  superficial  appearance  of  the  leaves  of 
Dodoncea  lobulata  are  quite  unlike  those  of  the  species  just  described. 


126  PLANT   HABITS   AND   HABITATS   IN   THE 

The  leaves  are  small,  linear,  or  linearcuneate.  They  are  well  coated 
with  some  substance,  probably  resinous,  which  causes  them  to  glisten 
in  the  light.  This  is  to  be  found  on  both  sides  of  the  leaves.  An  ex- 
amination of  the  leaf-structure  shows  that  the  two  sides  of  the  leaves 
are  nearly  alike,  if  not  wholly  so.  The  chlorenchyma  consists  of 
palisade  tissue  which  is  similar  on  the  two  sides.  Stomata  occur  on  both 
dorsal  and  ventral  surfaces  as  well  as  on  the  leaf  edges.  They  are 
somewhat  elevated  above  the  general  level  of  the  leaf,  especially  in 
the  young  leaves,  in  which  the  leaf-margin,  in  cross-section,  is  some- 
what crenulated.  Squat,  shield-shaped  trichomes  occur  on  both  leaf- 
surfaces.  These  are  multicellular  and  probably  glandular,  although 
they  were  so  few  in  the  material  examined  that  it  is  difficult  to  think 
that  the  resinous  covering  of  the  epidermis  was  wholly  derived  irom 
them,  especially  in  view  of  the  fact  that  the  secretion  is  very  equally 
distributed  over  the  leaf-surface  and  is  no  heavier  near  the  hairs  than 
at  some  distance  from  them.  No  sclerenchyma  was  found  in  the 
leaves  of  this  species. 

SOME  MORPHOLOGICAL  FEATURES  OF  THE  GENUS 
EREMOPHILA. 

The  species  of  Eremophila  must  be  considered  among  the  most 
interesting  and  in  certain  particulars  among  the  most  remarkable  of 
the  xerophytic  perennials  of  South  Australia.  They  occur  in  the 
drier  portions  of  the  state,  to  which  for  the  most  part  they  are  con- 
fined. The  species  are  shrubs  or  small  trees  and  nearly  all  of  those 
seen  bore  a  relatively  large  leaf-surface.  To  the  last  statement, 
however,  there  are  striking  exceptiops,  among  which  should  be  in- 
cluded PhoUdia  (formerly  Eremophila)  scoparia,  not  to  mention  others. 
Certain  of  the  species,  notably  E.  neglecta,  appear  to  be  confined  to 
the  desert,  although  others,  as  E.  brownii,  occur  in  the  arid  and  semi- 
arid  regions  as  well.  There  are  apparently  no  special  water-storage 
organs,  and  so  far  as  known  the  root-system  does  not  present  special 
characters.  In  several  of  the  species,  however,  as  will  appear  below, 
there  are  various  morphological  features  which  look  to  the  conserva- 
tion of  water,  once  it  is  taken  into  the  plants.  When  in  bloom  many  of 
the  species  are  of  striking  beauty. 

According  to  Solereder  (1899:706),  who  summarizes  the  earlier 
work  on  the  Myoporinese,  there  are  structural  features  of  interest 
in  species  of  Eremophila,  Thus,  the  leaves  and  the  stems  have  "Sekre- 
tenliicken,"  internal  glands,  which  I  am  calling  glandular  pockets,  as 
well  as  glandular  hairs  in  several  species.  Indeed,  such  are  wanting 
in  E.  longifolia  only.  Glandular  hairs  appear  generally  to  be  present 
and  to  vary  somewhat  in  form,  size,  and  structure.  The  other  type 
of  trichome,  a  "covering"  hair,  according  to  Solereder,  is  even  more 
variable.    It  may  consist  of  a  single  row  of  cells  which  may  be  branched 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  127 

or  aggregated  into  a  sympodial  type,  or  it  may  be  a  "water-storage" 
hair,  type  not  given,  or  a  disk  hair  with  multicellular  flattened  head. 
Stomata  occur  on  both  surfaces  of  the  leaves.  Strictly  bifacial  leaf- 
structure  does  not  occur  in  Eremophila. 

Apparently  much  of  the  work  referred  to  by  Solereder  was  based 
on  herbarium  material.  In  the  present  study,  also,  it  has  been  neces- 
sary to  rely  on  such  material.  The  following  species  of  Eremophila 
were  observed  by  the  writer  at  the  places  named  and  were  subsequently 
examined : 


Oodnadatta: 

At  Copley: 

At  Tarcoola: 

E.  alternifolia. 

L. 

alternifolia. 

E.  latrobei. 

brownii. 

brownii. 

paisleyi. 

freelingii. 

freelingii. 

rotundifolia, 

latrobei. 

latrobei. 

At  Ooldea: 

longifolia. 

longifolia. 

E.  alternifolia. 

neglecta. 

oppositifolia. 

oppositifolia. 

At  Quorn: 

paisley  i. 

E. 

brownii. 

rotundifolia. 

oppositifolia. 

Although  the  list  comprises  all  of  the  genus  that  were  seen  at  each 
of  the  places  named,  it  does  not  preclude  the  possibility  that  others 
may  have  been  at  each  station  as  well.  It  will  be  seen  that  E.  brownii 
is  fairly  widespread,  while  others,  as  E.  rotundifolia,  paisleyi,  and 
especially  neglecta,  have  a  limited  distribution.  No  species  of  the  genus, 
however,  appears  to  occur  outside  of  the  desert-arid  or  semi-arid 
regions. 

In  addition  to  the  species  of  Eremophila  as  at  present  understood, 
the  study  includes  Pholidia  scoparia,  formerly  classed  under  the  genus 
Eremophila.  This  species  has  a  greater  range  than  any  of  those  given 
in  the  above  list  and  occurs  where  the  rainfall  is  fairly  good  as  well  as 
where  it  is  relatively  small  in  amount. 

An  examination  of  the  leaves  of  the  different  species  of  Eremophila 
shows  not  a  little  diversity  as  to  several  morphological  features,  among 
which  are  the  conditions  of  hairiness,  the  character  of  the  trichomes, 
the  size,  the  plentifulness  as  well  as  the  presence  of  internal  secretion 
glands,  the  character  of  the  epidermis,  the  position  and  other  features 
of  the  stomata,  and,  not  to  extend  the  list,  the  character  of  the  sub- 
epidermal tissues.  There  are  also  apparent,  possibly  real,  correlations 
between  several  of  these  features  which  are  of  interest. 

Resinous  secretion  organs  occur  either  as  hairs  or  as  pockets  deeply 
embedded  in  the  tissues  of  leaf  or  stem.  In  the  leaves  the  pocket 
glands  are  usually  in  the  mesophyll,  although  the  position  is  not  con- 
stant. They  are  to  be  found  only  in  the  primary  cortex  of  stems. 
The  origin  of  these  internal  secreting  reservoirs,  for  such  they  appear 
to  be,  is  apparently  in  dispute.  It  is  maintained  on  one  side  that  they 
are  schizogenous  and  on  the  other  that  they  arise  through  the  breaking 


128  PLANT   HABITS   AND   HABITATS   IN   THE 

down  of  cell-walls.  But  according  to  Solereder,  inasmuch  as  the 
secretion  reservoirs  are  surrounded  by  an  epithelium  several  cells  in 
thickness,  the  innermost  walls  of  which  ultimately  become  dissolved, 
freeing  the  resinous  substance,  the  gland  is  to  be  considered  as  being 
schizolysigenous.  Pocket  glands  of  this  character  were  found  in  all 
of  the  species  of  Eremophila  examined  except  E.  longifoUa,  thus  sup- 
porting the  results  of  von  Bokorny  (Solereder,  1899:706).  Glands 
of  this  kind  were  not  seen  in  the  stems  of  E.  oppositifolia  in  the  material 
available  for  examination  by  me,  but  they  should  be  expected  to  occur 
in  them  as  long  as  they  have  been  surely  found  in  the  leaves. 

The  glandular  trichomes  exhibit  some  variation  as  between  different 
species.  They  may  be  either  short,  as  they  usually  are,  or  have  a 
stalk  of  several  cells.  The  heads  may  either  be  flattened  or  somewhat 
elongated.  The  glandular  hairs  of  E.  neglecta  and  of  E.  freelingii  are 
of  the  former,  and  those  of  E.  rotundifolia  are  of  the  latter  type. 
Glandular  hairs  were  found  in  all  of  the  species  examined  except 
E.  longifoUa,  E.  oppositifolia,  and  Pholidia  scoparia.  So  far  as  the 
resinous  secretion  of  the  hairs  is  concerned,  it  was  seen  to  be  more  or 
less  abundant  on  the  leaves  and  stems  wherever  the  hairs  were  to  be 
found,  but  only  in  E .  freelingii  was  it  found  to  be  copious.  In  specimens 
of  this  species  from  Oodnadatta,  and  especially  on  the  stems,  the 
resinous  exudation  was  so  abundant  as  to  quite  cover  the  glandular 
hairs  themselves.    It  was  also  present  in  large  amount  on  the  leaves. 

Stomata  were  found  on  both  sides  of  the  leaves  of  all  of  the  species 
examined.  In  most  cases  they  were  flush  with  the  leaf-surface.  How- 
ever, in  the  leaves  of  such  as  had  a  heavy  covering  of  hairs,  as  for 
example  in  E.  rotundfolia,  the  guard-cells  projected  somewhat.  It 
was  noticeable,  also,  that  a  similar  condition  obtained  in  E.  freelingii, 
where  the  resinous  coating  of  the  leaf  was  heavy.  In  either  instance 
it  is  apparent  that  this  superior  position  of  the  stomata  is  directly 
related  to  the  heavy  protective  cover  of  the  leaf. 

A  heavy  cuticle  was  found  to  be  present  on  the  leaves  of  most  species, 
but  it  is  heavier  in  some  than  in  others,  and  this  feature  is  usually 
con  elated  with  the  presence,  or  absence,  of  a  resinous  covering  or 
one  of  trichomes.  Where  such  is  largely  or  wholly  absent,  as  in 
E.  brownii,  alternifolia,  and  paisleyi,  the  cuticle  is  especially  heavy. 
In  the  case  of  the  last  two  species  the  cuticle  is  so  heavy  that  it  brings 
about  a  rigid  condition  of  the  leaf  itself.  In  the  case  of  E.  rotundifolia, 
however,  where  the  hairy  leaf-coveiing  is  particularly  heavy,  as  will 
be  mentioned  below,  the  cuticle  is  very  light. 

The  structure  of  the  leaves  is  generally,  although  apparently  not 
exclusively,  dorsiventral.  Thus,  palisade  cells  are  usually  to  be  found 
on  the  dorsal  and  not  on  the  ventral  side.  In  Pholidia  scoparia, 
Eremophila  latrobei,  E.  longifoUa,  E.  paisleyi,  E.  alternifolia,  and  E. 
oppositifolia,   however,   either  palisade  cells  similar  in  appearance 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  129 

are  on  both  sides  of  the  leaves,  or  there  is  but  little  difference  between 
the  dorsal  and  the  ventral  sides  in  this  regard.  The  leaf-structure 
of  E.  rotundifolia  is  also  dorsiventral.  In  this  species  there  is  no  well- 
marked  palisade,  but  fairly  small  cells,  somewhat  elongated  in  a  di- 
rection at  right  angles  to  the  leaf-surface,  constitute  a  distinct  stratum 
on  both  sides  of  the  leaf.  The  cells  of  these  strata  have  the  appearance 
of  palisade  cells  which  have  undergone  division  by  cross-walls  sub- 
sequent to  the  formation  as  such,  but  this  procedure  probably  did 
not  take  place.  A  somewhat  similar  condition,  but  not  so  noticeable, 
is  to  be  seen  in  E.  negleda.  As  will  appear  presently,  only  in  Pholidia 
scoparia  and  in  Eremophila  longifoUa,  of  the  species  having  well- 
defined  palisade  tissue,  is  there  a  covering  of  hairs.  In  the  latter 
species  the  covering  is  sparse  and  in  the  former  it  is  of  a  peculiar  type 
and  not  heavy.  The  correlation  between  leaf-cover  and  the  presence 
of  palisade  tissue  and  the  dorsiventral  condition  of  the  leaf  apparently 
breaks  down  in  E.  oppositifolia,  which  has  both  of  these  features,  the 
cover  hairs  being  present  in  abundance.  It  was  noted,  also,  that  the 
walls  of  the  epidermis  of  the  species  were  heavy.  All  of  these  features 
might  point  to  the  need  of  relatively  good  water-relations  of  the  species, 
but  this  remark  needs  further  observation  to  substantiate  it. 

The  cover-hairs  are  various.  In  E.  freelingii  they  consist  of  a  single 
row  of  cells  with  fairly  heavy  walls.  The  cover-hairs  of  E.  brownii 
appear  to  be  only  of  this  kind,  although  Solereder  states  that  branched 
trichomes  occur  in  the  species.  Both  the  simple  and  the  branched 
types  of  cover-hairs  weie  found  in  E.  neglecta  stems,  although  only 
the  former,  and  that  sparingly,  occur  on  the  leaves  of  the  species. 
In  E.  alternifolia  (fig.  18)  and  rotundifolia  theie  were  no  proper  tri- 
chomes of  either  kind  above  described,  but  the  epidermal  cells  of  the 
young  stems,  and  not  of  the  leaves,  project  as  short  papillse.  In  E. 
neglecta  there  appear  to  be  such  papillate  cells  also,  but  not  to  the 
exclusion  of  cover-hairs  and  not  in  abundance.  In  the  two  species 
mentioned  such  epidermal  cells  are  wanting  in  the  leaves,  nor  are  cover- 
hairs  present.  It  is  possible,  therefore,  that  the  papillate  cells  may  be 
considered  as  simple  cover-hairs.  The  leaves  and  stem  of  Pholidia 
scoparia  bear  shield-shaped  trichomes  which  generally  have  a  short 
stalk  and  are  closely  pressed  to  the  leaf-surface.  In  young  leaves  and 
stems,  at  least,  they  overlap  and  form  a  very  perfect  cover. 

FUSANUS   ACUMINATUS. 

The  leaves  of  Fusanus  acuminatus  are  fairly  large,  narrow-lance- 
olate, and  rather  thick.  There  appears  to  be  no  structural  difference 
between  the  dorsal  and  the  ventral  sides.  The  following  may  be  said 
to  be  the  most  striking  structural  features  of  the  leaves:  The  chlor- 
enchyma  consists  of  relatively  short  palisade  cells  which  maintain  this 
character  throughout.     Crystals  are  to  be  found  scattered  through  the 


130  PLANT  HABITS   AND   HABITATS   IN   THE 

mesophyll.  There  is  little  mechanical  tissue,  and  what  there  is  consists 
of  cells  with  prominent  lumen,  both  in  connection  with  the  conductive 
tissue  and  at  the  leaf  margins.  The  epidermis  is  made  of  two  cell- 
layers  of  which  the  walls  are  fairly  heavy.  Stomata  occur  on  both 
leaf-surfaces.  An  additional  feature  may  be  mentioned,  namely,  the 
presence  of  tracheids  apparently  independent  of  the  regular  conductive 
tissue  (fig.  22).  Very  possibly  they  may  be  considered  to  have  the 
capacity  of  storing  water,  as  in  instances  which  are  well  known. 

Gravillea  stenobotrya. 
The  leaves  of  Gravillea  stenobotrya  are  narrow-linear  and  placed 
upright  on  the  branches.  They  have  unlike  dorsal  and  ventral 
sides  which  are  apparently  subject  to  quite  similar  conditions  of  light 
and  evaporation.  A  cross-section  of  the  leaf  shows  certain  striking 
structural  features  (fig.  24).  The  leaf  margins  are  in-rolled,  giving 
a  rounded  dorsal  and  a  channeled  ventral  aspect.  On  the  dorsal  side 
the  epidermis  is  especially  heavy,  owing  to  the  great  length  of  its 
component  cell,  and  the  cuticle  also  is  heavy,  but  on  the  ventral  side 
the  epidermis  is  not  heavy  and  the  cuticle  is  light.  Few  if  any  trichomes 
occur  on  the  dorsal  surface,  while  the  ventral  side  is  heavily  clothed 
with  hairs,  all  apparently  of  the  two-armed  type  figured  and  described 
by  Solereder  (1899:803).  Stomata  are  confined  to  the  ventral  side. 
The  chlorenchyma  is  heavier  on  the  dorsal  than  on  the  ventral  side. 
Sclerenchyma  is  associated  with  the  conductive  tissue,  but  is  not 
especially  abundant.  The  ground  tissue  in  the  material  studied  ap- 
pears to  be  of  a  fairly  loose  structure  and  is  not  heavily  walled. 

Hakea  multilineata  and  H.  leucoptera. 

The  leaves  of  Hakea  multilineata  are  long,  narrow,  and  placed  in  a 
vertical  position  on  the  shrub.  They  are  striate  and  have  a  very 
tough  texture.  A  cross-section  shows  that  the  two  sides  are  similar 
(fig.  27).  The  following  are  the  most  striking  structural  features  of 
the  leaves:  The  chlorenchyma  extends  from  side  to  side.  Separating 
the  chlorenchyma  into  strips  are  ribbons  of  sclerenchyma  which  reach 
from  the  fibro-vascular  bundles  of  the  middle  portion  of  the  leaf  to 
the  epidermis  of  either  face.  The  sclerenchyma  appears  to  be  mainly 
or  wholly  fibrous.  The  chlorenchyma  is  composed  of  relatively  long 
and  narrow  palisade  cells.  The  epidermis  is  heavy  and  has  a  heavy 
cuticle.  The  stomata  are  situated  at  the  level  of  the  inner  epidermal 
walls  and  hence  at  the  bottom  of  pores  made  by  the  thickened  outer 
portion  of  the  epidermis  (fig.  28). 

In  H.  leucoptera  the  leaves  are  cylindrical,  with  the  end  tapering 
to  a  point,  hence  the  common  name  "needle"  bush.  The  chlorenchyma 
forms  an  uninterrupted  band  beneath  the  epidermis.  The  central 
portion  of  the  leaf  has  scattering  bundles  of  conductive  tissue,  each 
with  its  accompanying  mass  of  sclerenchyma  on  opposite  sides, 
and  all  surrounded  by  a   fairly  heavy  walled   parenchyma.     The 


ARID    PORTIONS   OF    SOUTH   AUSTRALIA.  131 

effect  is  as  if  the  mechanical  tissue  referred  to  were  embedded  in  the 
parenchyma,  as  in  fact  it  is.  At  the  periphery  of  this  centrally  located 
cell-mass  are  separated  hard-bast  fibers  which  resemble  the  palisade 
cells  of  the  chlorenchyma  in  diameter  and  usually  in  length,  and  which 
extend  through  the  chlorenchyma  to  the  epidermis  (fig.  26).  Al- 
though these  fibers  occasionally  extend  well  into  the  centrally  placed 
tissue,  they  nevertheless  are  almost  wholly  confined  to  the  chloren- 
chyma. The  fibers  also  are  usually  simple  and  not  branched.  In  these 
two  particulars  they  appear  to  be  unlike  the  sclerenchyma  of  a  similar 
nature  described  by  Jonsson  and  referred  to  by  Solereder  (1899:801), 
in.  which  branching  occurs,  and  which  is  generally  scattered  through- 
out the  leaf. 

The  epidermis  is  unusually  heavy,  owing  to  the  greatly  thickened 
cuticle.  The  stomata  are  placed  on  a  level  with  the  inner  wall  of  the 
epidermis  and  are  thus  at  the  bottom  of  a  chimney-like  structure 
composed  of  the  epidermis,  mainly  of  the  cuticle  (fig.  26).  At  the 
inner  portion  of  the  stomatal  pore,  and  immediately  above  the  stomata, 
are  thickened  papillae  of  cell-wall  material;  these  fairly  well  close 
the  bottom  of  the  stomatal  pores  (fig.  26). 

In  the  mature  leaves,  both  of  H.  multilineata  and  of  H.  leucoptera, 
there  do  not  appear  to  be  trichomes  of  any  kind,  but  the  remains  of 
hairs  are  occasionally  met  with,  showing  that  when  young  the  leaves 
are  provided  with  them.  In  the  last  figure  referred  to,  the  position 
of  a  trichome  is  indicated  by  the  indentation  to  the  left  of  the  stomatal 
pore,  brought  about  by  the  failure  of  cuticle  to  form  where  the  hair 
was  situated.  An  additional  note  should  be  made  on  the  stomatal 
pores.  In  the  material  studied  there  often  appear  to  be  pores  which 
are  continuous  with  one  another,  with  the  effect  that  a  stomatal  chamber 
containing  more  than  one  pore  is  formed. 

Melaleuca  parviflora. 

The  leaves  of  Melaleuca  parviflora  are  short  and  narrow,  being  about 
1  mm.  in  width  and  9  mm.  in  length.  A  transverse  section  of  the 
leaves  shows  the  following  leading  structural  features:  There  is  a 
well-defined  chlorenchyma,,  consisting  of  narrow  and  fairly  long  pali- 
sade cells,  which  is  similar  on  both  leaf-sides.  The  leaf  interior  is 
composed  mostly  of  chlorophyll-free  parenchyma,  of  good  size,  which 
has  fairly  thick  walls  and  no  or  few  intercellular  spaces.  Sclerenchyma 
is  to  be  found  associated  with  the  conductive  tissue  only,  and  it  is  not 
a  conspicuous  feature.  The  epidermis  has  a  fairly  thick  outer  wall. 
The  stomata  are  on  both  leaf-surfaces  and  lie  at  the  bottom  of  pores 
made  of  the  thickened  cuticle  of  the  epidermis. 

PiTTOSPORUM    PHILLYR^OIDES. 

Thelesives of  Pittosporum  phillyrceoides  are  linear-oblong,  about  8  mm. 
in  width  and  120  mm.,  more  or  less,  in  length.  The  small  tree  is  well 
covered  with  them,  so  that  the  evaporation  surface  is  not  inconsiderable. 


132  PLANT   HABITS   AND   HABITATS   IN   THE 

There  is  a  distinct  bifacial  structure  of  the  leaves  of  this  species 
of  Pittosporum.  The  stomata  are  confined  to  the  ventral  side.  The 
chlorenchyma  of  the  dorsal  side  is  more  consistently  of  palisade  cells 
than  is  that  of  the  other.  The  stomata  are  on  a  level  with  the  epi- 
dermis. Crystals  are  fairly  numerous  in  the  mesophyll.  A  relatively 
small  amount  of  sclerenchyma,  not  well  developed,  is  to  be  found  in 
connection  with  the  main  conductive  tracts  and  on  the  leaf-edges. 
But  the  most  striking  feature  of  the  structure  of  the  leaves  is  the 
presence  of  an  epidermis  on  the  dorsal  side,  consisting  of  more  than 
one  cell-layer.  The  outer  epidermal  cells  are  approximately  one-fifth 
as  deep  as  the  underlying  epidermal  cells,  and  these  are  occasionally 
accompanied,  as  shown  in  figure  29,  by  narrow  cells  which  appear  to 
be  situated  in  their  outer  walls.  The  two-celled  condition  of  the 
epidermis  continues  around  the  edges  of  the  leaves,  and  a  few  epidermal 
cells  on  the  ventral  side  may  be  of  two  layers.  On  both  ventral  and 
dorsal  surfaces  the  outer  epidermal  wall  is  very  thick,  and  the  inner 
walls  of  the  epidermis  on  both  leaf-sides  are  also  somewhat  thickened 
(fig.  30). 

Triodia  irritans. 

The  occurrence  of  Triodia  throughout  the  driest  portion  of  the  in- 
terior of  the  continent,  characteristically  in  sandy  habitats,  makes  the 
structure  of  especial  interest.  T.  irritans  is  a  "bunch"  grass,  with 
fairly  rigid,  sharp-pointed  leaves.  It  is  sometimes  called  "porcupine" 
grass,  which  aptly  suggests  its  nature. 

A  cross-section  of  a  leaf  of  Triodia  is  nearly  circular  in  outline. 
This  is  due  to  the  in-rolling  by  which  the  ventral  surface  comes  to  lie 
within,  and  only  the  dorsal  surface  is  presented  to  the  outside  (fig.  31). 

On  the  dorsal  outer  as  well  as  the  inner  surfaces  are  several  deep 
furrows,  giving  the  leaf-surface  a  convoluted  effect.  The  chloren- 
chyma is  segregated  on  either  side  of  the  furrows,  so  that  in  section 
the  chlorophyll-bearing  tissue  occurs  in  separate  masses.  Scleren- 
chyma constitutes  a  very  prominent  part  of  the  tissues  of  the  leaf. 
On  the  dorsal  side  it  reaches  to  the  epidermis  and  extends  to  about  the 
depth  attained  by  the  chlorenchyma,  and  on  the  ventral  inner  side  it 
also  reaches  to  the  epidermis  but  does  not  occupy  much  of  the  spaces 
between  masses  of  chlorenchyma,  which  is  filled  in  with  parenchyma 
having  faiily  heavy  walls.  The  outer  epidermal  wall  is  heaviest  in 
the  furrows,  but  is  not  especially  heavy  elsewhere.  Trichomes  are 
present  sparingly  on  the  in-rolled  surface  and  short  hairs  close  the 
narrowed  "throat"  of  the  fuirows.  Stomata  are  small  and  confined 
to  the  portion  of  the  furrows  opposite  the  chlorophyll-bearing  cells, 
and  are  present,  but  not  in  abundance,  on  both  leaf-surfaces. 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  133 

CERTAIN  REACTIONS  AND  ADJUSTMENTS  OF  PLANTS  OF 
THE  MORE  ARID  PORTIONS  OF  SOUTH  AUSTRALIA. 

Any  conception  of  the  nature  of  the  reactions  of  living  plants  to 
their  physical  environment,  as,  for  example,  to  any  particular  feature 
of  their  environment  like  the  oxygen-supply  or  that  of  water,  has  to 
deal  with  factors  widely  different  from  a  simple  or  direct  reaction  in 
which  non-living  substances  only  take  part.  Aside  from  and  in  addi- 
tion to  the  chemical  complexity  of  the  living  organism,  the  feature  of 
its  heredity  must  be  taken  into  account.  This,  to  put  it  in  simple 
terms,  merely  means  in  the  course  of  its  phylogeny  the  organism  has 
for  untold  ages  reacted  to  its  environment,  so  that  the  living  plant, 
which  to-day  occupies  its  place  in  the  desert,  is  in  itself  a  resultant, 
so  to  speak,  of  all  of  the  reactions  of  its  long  past.  One  of  the  results 
is  that  living  plants  with  unlike  histories,  in  the  sense  above  used, 
may  react  along  different  lines  to  a  certain  extent,  according  to  the 
direction  of  the  development  they  may  be  taking.  But  in  the  present 
study  only  existing  plants  and  the  present-day  environment  are  taken 
into  consideration,  and  the  following  paragraphs  give  some  of  the  most 
striking  reactions  of  the  plants  to  their  environment.  Other  reactions 
are  referred  to  in  the  course  of  the  paper. 

Reactions  to  Light. 

Among  the  possible  reactions  to  light  may  be  mentioned  the  vertical 
position  assumed  by  the  chlorophyll-bearing  organs  of  many  or  most 
perennials  of  the  drier  portions  of  the  state.  This  is  attained  in  part 
by  an  upright  position  of  the  branches,  but'  mainly  by  a  vertical  posi- 
tion taken  by  the  individual  organs  themselves  and  in  a  measure 
independent  of  the  position  of  the  branches  which  bear  them.  In 
Hakea  multilineata,  GraviUea  stenobotrya,  and  Acacia  linophyUa,  to 
mention  no  others,  the  vertical  position  is  attained  because  of  the 
upright  habit  of  the  leaves,  and  in  Pittosporum  phillyrceoides  and 
Eucalyptus  spp.  it  is  attained  by  their  dependence. 

The  presence  of  a  heavy  epidermis,  or  of  a  covering  of  trichomes, 
or  of  resinous  substances,  or  the  elongation  of  the  cells  containing 
chlorophyll  bodies  in  a  diiection  at  right  angles  to  the  surface  of  the 
leaf,  may  all  (in  part  at  least)  be  related  to  an  adjustment  of  the  organ 
to  the  intensity  of  the  light.  The  evidence  for  certain  of  these  con- 
clusions, it  must  be  said,  is  merely  inferential.  For  example,  in  Ere- 
mophila  rotundifolia  the  leaves  have  a  heavy  covering  of  trichomes,  and 
in  them  the  palisade  cells  are  poorly  developed.  The  palisades  appear 
to  be  about  the  same  in  E.  neglecta,  in  which  species  there  is  a  heavy 
epidermis  with  glandular  hairs  and  with  a  marked  resinous  coating. 

Whether,  however,  the  light-screen  of  whatever  kind  is  a  cause  or 
effect  is  another  question,  and  the  observations  throw  no  light  on  its 
solution.     The  interactions  and  interrelations  are  so  complex  that 


134  PLANT  HABITS   AND   HABITATS   IN   THE 

their  disentanglement  is  not  without  its  difficulties.  For  example, 
in  Triodia  irritans  the  large  development  of  mechanical  tissue,  as  will 
appear  below,  is  probably  directly  related  to  the  physical  and  chemical 
effects  of  dryness,  but  the  position  of  this  tissue  in  the  leaves  is  such 
that  it  becomes  a  very  effective  light-screen  for  the  chlorenchyma, 
which  is  not  of  palisade  cells,  of  the  leaf.  And  from  the  last  circum- 
stance it  might  be  considered  to  be  closely  associated  in  some  way 
with  the  light  relations  of  the  plant — which  indeed  may  be  the  case, 
but  this  remains  to  be  proved. 

Reactions  to  Temperature. 

The  most  apparent  reactions  of  the  plants  to  temperature  have  to 
do  with  the  recurrence  of  vegetative  growth  and  of  activities  associated 
with  the  formation  of  flowers  and  fruits.  But  also  the  general  distribu- 
tion of  plants,  particularly  the  north-south  distribution,  is  largely 
dependent  on  temperatures.  Often,  also,  local  distribution,  especially 
aspect  "preference,"  is  directly  related  to  the  same  as  well.  Aside 
from  these  well-known  reactions,  which  are  of  great  importance, 
few  appear  to  have  been  definitely  established.  Temperature  is  ef- 
fective indirectly,  however,  in  that  it  is  directly  related  to  the  relative 
humidity  of  the  air  and  may  greatly  affect  the  moisture-content  of 
the  soil  as  well.  Slopes,  therefore,  which  receive  the  most  heat  may 
also  be  the  most  arid  both  as  regards  the  soil  and  the  air.  The  effects 
of  temperature  on  various  chemical  processes  in  the  plant  have  already 
been  referred  to  and  need  not  be  sunamarized  in  this  place. 

Reactions  to  a  Small  Water-supply. 

A  reduction  of  the  leaf-surface  is  the  most  noticeable  effect  on 
the  perennial  plants  of  a  small  water-supply  with  its  direct  accom- 
panying physical  features,  a  low  relative  humidity  of  the  air,  and  a 
rapid  rate  of  evaporation.  This  reaction  is  shown  in  several  ways. 
Trees  are  usually  small  and  symmetrical.  The  "canopy"  form  of 
such  of  the  Eucalyptus  species  as  have  a  facultative  "mallee"  habit 
more  especially,  of  which  E.  oleosa  is  an  example,  illustrate  this,  al- 
though it  can  be  seen  at  every  turn  in  the  drier  portions  of  South  Aus- 
tralia. Where  the  species  grow  by  stream  ways  the  habit  of  growth  is 
usually  noticeably  less  compact.  Often,  usually  in  the  drier  regions, 
the  foliage  is  confined  to  the  tips  of  the  branches,  by  which  the 
canopy  effect  is  heightened.  The  immediate  effect  on  the  plants, 
however,  is  to  limit  the  growth  of  the  leaves  or  to  bring  about  such  a 
modification  of  the  chorophyll-bearing  organs  as  is  to  be  witnessed  in 
many  acacias,  or  to  wholly  suppress  the  formation  of  leaves  in  mature 
plants.  During  this  process  the  foliar  organ  apparently  undergoes 
an  alteration  in  form,  so  that  it  becomes  relatively  long  as  compared 
with  what  may  be  supposed  to  be  the  ancestral  condition,  or  that 
of  plants  more  favorably  situated  as  regards  the  water-supply.  This 
observation  was  directly  confirmed  by  numerous  measurements  and 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  135 

indirectly  by  a  possible  reversion  of  the  phyllodia  of  Acacia  pycnantha, 
for  example,  which  are  relatively  large.  This  species  apparently  re- 
quires relatively  good  water-relations. 

The  vertical  position  assumed  by  the  foliar  organs  of  shrubs  and 
trees  in  the  dry  regions  is  perhaps  mainly  due  to  a  reaction  to  condi- 
tions accompanying  a  small  water-supply,  although  possibly  there  is 
here,  as  mentioned  above,  a  light-relation  of  moment.  Among  the 
species  having  this  characteristic  especially  well  developed  are  Hakea 
multilineata,  Gravillea  stenobotrya,  Acacia  linophylla,  A.  tarculiensis, 
Pittosporum  phillyrceoides,  and  Eucalyptus  spp. 

A  frequent  accompaniment  of  a  condition  of  dryness  in  the  environ- 
ment, and  possibly  often  directly  related  to  it,  is  the  presence  of  a 
covering  of  trichomes  which  serves  the  end  of  protecting  the  foliar 
organs  against  excessive  evaporation,  as  well  as  against  intense  illum- 
ination. The  trichomes  are  of  two  general  kinds,  those  which  serve 
merely  as  a  covering  and  those  which  are  glandular.  A  heavy  covering 
of  the  former  usually  produces  a  gray-green  effect.  Among  species 
having  such  a  trichomal  covering  well  developed  are  Acacia  linophylla, 
Eremophila  longifolia,  E.  oppositifolia,  and  E.  rotundifolia.  In  certain 
species,  as  in  Gravillea  stenobotrya,  the  (mature)  leaves  have  a  covering 
of  hairs  on  the  ventral  surface  only,  and  in  other  plants  with  furrows  in 
the  leaves  or  phyllodia  such  trichomes  may  be  confined  to  the  furrows, 
as  in  Casuarina  sp.  and  Triodia  irritans,  at  least  in  the  mature  organs. 

Glandular  hairs  are  frequently  observed.  They  are  numerous,  for 
example,  in  Acacia  linophylla,  Casuarina  stricta,  and  Dodoncea  sp.,  but 
may  possibly  be  found  in  most  perennials  of  the  dry  regions,  at  least 
in  the  young  stems  and  leaves,  or  their  equivalent.  In  Acacia  tarcu- 
liensis  may  be  seen  what  appears  to  be  glandular  trichomes,  but  they 
are  restricted  to  the  margins  of  the  phyllodia. 

The  formation  of  resinous  secretions  and  secretions  of  oil,  etc.,  by 
glandular  trichomes  as  well  as  by  internal  glands,  is  of  frequent  oc- 
currence in  plants  of  the  drier  regions.  It  is  possibly  in  some  way 
directly  related  to  the  dryness  of  the  environment,  although  in  exactly 
what  way  seems  doubtful.  Internal  glands  occur  in  the  Myrtaceae,  as 
is  well  known,  but  may  be  found  in  other  families,  as  for  example, 
in  the  Myoporineae.  In  several  species  of  the  genus  Eremophila  of 
the  family  last  named,  internal  secretion-glands  were  seen  in  the  leaves 
and  in  the  cortex  of  the  young  stems. 

Other  morphological  features  also  are  apparently  mainly  associated 
with  the  occurrence  of  the  species  under  dry  climatic  conditions. 
In  all  or  nearly  all  species  of  perennials,  for  example,  the  epidermis 
is  very  heavy.  This  is  usually  brought  about  by  the  great  thickness 
of  the  outer  wall,  which  is  probably  always  cutinized,  but  in  Pittos- 
porum phillyrcBoides  and  Fusanus  acuminatus  the  epidermis  is  in  part 
or  altogether  of  two  or  more  layers  of  cells.  On  the  dorsal  side  of  the 
leaves  of  Gravillea  stenobotrya  the  epidermal  cells  have  unusual  length. 


136  PLANT   HABITS   AND    HABITATS    IN   THE 

Usually  the  lateral  walls  as  well  as  the  internal  wall  of  the  epidermal 
cells  are  considerably  thickened. 

A  structural  characteristic  of  note  in  marked  xerophytes  is  the 
prominent  development  of  cell-walls  or  of  tissue  with  heavy  walls. 
Sclerenchyma  of  whatever  kind  is,  in  fact,  usually  to  be  found  in  the 
foliar  organs  and  occasionally  in  abundance.  In  Triodia  irritans,  for 
example,  it  constitutes  a  very  large  proportion  of  the  tissue  of  the  leaf, 
but  it  is  a  marked  feature  in  the  leaves  of  Hakea  multilineata  and 
H.  leucoptera,  as  well  as  in  the  phyllodia  of  Acacia  linophylla  and  other 
species  of  the  genus.  The  pronounced  development  of  cell-walls  is  a 
direct  effect  of  drying  conditions,  as  shown  elsewhere. 

In  connection  with  the  subject  of  the  formation  of  heavy  cell-walls 
and  of  mechanical  tissue,  it  is  pertinent  to  remark  here  that  the  writer 
was  struck  with  the  scarcity  of  the  quality  of  spininess  in  such  peren- 
nials as  he  saw  in  the  drier  portions  of  South  Australia.  Aside  from  the 
"needle  bush,"  Hakea  leucoptera,  the  "myall,"  Acacia  rigens,  and  the 
"dead  finish"  A.  tetragonophylla,  whose  leaves  or  phyllodia  are  spinose, 
and  A.  continua  with  spinescent  branches,  the  writer  does  not  recall 
having  seen  any  perennials  with  very  prominent  spines.  Other 
acacias  with  spinose  phyllodia  or  branches,  or  with  small  spines, 
morphologically  stipules,  may  be  met  with,  but  nowhere  in  the  drier 
portions  of  South  Australia  is  there  to  be  found  anything  like  the  large 
development  of  spines  as  a  characteristic  of  the  perennial  plants  that 
one  encounters,  for  example,  in  southern  Arizona. 

The  chlorenchyma  of  the  foliar  organs  is  usually  composed  of  pali- 
sade cells.  This  however,  is  not  without  its  exceptions;  for  example, 
in  Eremophila  rotundifolia  the  chlorenchyma  is  of  short  cells.  In  this 
species  the  leaves  are  heavily  covered  with  trichomes.  There  thus 
appears  to  be  some  relation  between  the  presence  of  the  one  and  the 
development  of  the  other.  In  other  species,  however,  as  in  Eremophila 
longifolia,  there  are  both  palisades  and  trichomes,  and  a  similar  condi- 
tion is  to  be  found  in  Acacia  linophylla,  not  to  mention  others. 

Reactions  to  the  Subterranean  Environment. 

Relatively  little  is  known  concerning  the  direct  reaction  of  the  plants 
of  the  drier  portions  of  South  Australia  to  the  soil  and  soil  conditions, 
yet  the  subject  is  recognized  as  of  much  importance.  Thus  the  presence 
of  halophytes,  which  constitute  an  important  part  of  the  flora  of  the 
far  north,  is  directly  related  to  an  excess  of  salts  in  the  soil  solution. 
This  feature  has  been  brought  about  in  some  way  by  the  development 
on  the  part  of  the  plants  of  the  quality  of  tolerance  to  a  highly  con- 
centrated soil  solution.  In  this  development  an  important  element 
is' the  formation  of  plant  juices  of  high  concentration  and  therefore 
of  high  osmotic  values. 

The  reaction  of  plants  to  the  physical  nature  of  the  soil  per  se  is 
probably  also  of  importance.  In  coarse  soils  (as  in  sand)  quick  and 
fairly  deep  penetration  of  the  rains  and  the  formation  of  a  dust 


ARID   PORTIONS   OF   SOUTH   AUSTRALIA.  137 

mulch  by  which  the  water  absorbed  is  well  retained  aie  prominent 
features  in  the  water  relations.  Their  relatively  high  temperatures 
and  the  quaUty  of  good  aeration  are  also  to  be  considered.  In  the 
\icinity  of  Oodnadatta,  especially,  where  the  observations  were  mostly 
made,  it  was  found  that  the  roots  of  species  growing  on  the  dunes 
had  a  fairly  superficial  type  of  root-system  and  that  the  roots  extended 
far  from  the  base  of  the  stem.  Whether,  however,  the  same  species 
growing  under  other  soil  conditions  developed  another  type  of  root- 
system  was  not  learned. 

The  foliage  of  species  growing  on  the  sand  dunes  exhibits  charac- 
teristics of  pronounced  xerophytes,  which  may  have  been  in  part 
attributable  to  the  brilliancy  of  the  light,  increased  by  reflection 
from  the  surface,  and  not  wholly  to  the  small  water-supply.  The  soils 
in  other  regions,  for  example  at  Copley,  are  in  part  of  a  very  fine 
texture,  but  whether  the  flora  to  be  found  on  such  soils  is  confined  to 
them  or  is  modified  in  any  determinable  way  by  them,  was  not  learned. 
However,  from  the  observations  of  Osborn  (1914:114)  more  especially, 
which  were  made  in  the  Mount  Lofty  Ranges  near  Adelaide,  it  might 
be  expected  that,  in  the  drier  portions  of  the  state  also,  soils  of  unlike 
texture  would  support  dissimilar  floras.  The  entire  question  regarding 
the  relation  of  plants  to  the  physical  nature  of  the  soil,  it  may  be  said, 
is  so  closely  connected  with  the  temperature,  moisture,  and  aeration 
of  the  soil,  all  of  which  are  directly  influenced  by  its  texture,  that  to 
separate  the  special  effects  of  the  physical  nature  merely  from  the 
balance  would  be  a  difficult  matter. 

The  amount  of  moisture  in  the  soil  plays  a  very  important,  not  to 
say  a  leading,  role  among  the  environmental  factors  of  the  plants  of 
the  dry  portions  of  the  state.  Although  this  is  well  known  and  gener- 
ally recognized,  particular  reference  to  certain  plant  reactions  to 
soil  moisture  may  not  be  out  of  place.  The  limit  of  root  penetration 
may  coincide  with  the  depth  of  the  penetration  of  the  rains,  or  of  water 
derived  from  the  rains,  as  in  very  dry  regions.  For  this  reason,  in 
regions  where  the  general  penetration  of  the  rains  is  slight,  the  placing 
of  the  roots  of  perennials  is  necessarily  superficial.  In  this  connection 
it  is  of  interest  to  note  the  belief  among  the  wheat-growers  of  the 
central  portion  of  the  state,  as  communicated  by  one  of  them,  that 
wheat  soil  when  thoroughly  moistened  to  a  depth  of  one  meter  contains 
sufficient  water  to  mature  the  crop. 

In  certain  species,  especially  in  Kochia  sp.,  filamentous  rootlets 
are  to  be  found  on  the  main  laterals  which  arise  very  soon  after  the 
soil  has  been  moistened  by  the  rains  and  which  cease  to  function  when 
the  ground  is  dry.  These  occur  in  groups  and  serve  the  purpose  of 
quickly  and  very  considerably  increasing  the  absorption  surface  of 
the  roots.  They  are,  in  fact,  ''deciduous"  roots  and  are  analogous  to 
such  roots  as  are  found  in  many  perennials  of  southern  Arizona. 


138  PLANT  HABITS  AND  HABITATS  IN  THE 

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Fuller,  G.  D.     1918.     Raunkiaer's  "leaf  forms,"   "leaf-size  classes,"  and  statistical 

methods.     Plant  World,  vol.  21,  p.  30. 
Gregory,  J.  W.     1906.     The  dead  heart  of  AustraUa.     A  journey  around  Lake  Eyre  in 

the  summer  of  1901-1902,  with  some  account  of  the  Lake  Eyre  basin  and  the  flowing 

wells  of  central  AustraUa. 

.     1916.     Australia. 

Hann,  J.     1903.     Handbook  of  cUmatology.     Eng.  trans. 

Harris,  A.  J.     1915.     The  osmotic  pressure  of  vegetable  saps  in  i^elation  to  local  environ- 
mental conditions  in  the  Arizona  deserts.     Carnegie  Inst.  Wash.  Year  Book  No.  14. 
,  J.  V.  Lawrence,  and  R.  A.  Gortner.     1916.     The  cryoscopic  constants  of  ex- 
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climate  and  plant-growth  in  humid  and  arid  regions. 
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^•ii'.-^ 


■£ii,mi^^^h 


A.  \"ie\v  luoking  iiuith  from  O'Halloran's  Mount,  Oodnadatta,  showing  luwur  plaiii,  wuh  upper 

plain  at  extreme  right  in  background. 

B.  Lower  plain  near  Oodnadatta,  showing  "gibbers"  on  the  surfac3  and  typical  depression,  with 

species  of  Eremophila. 


A.  Eremopliila  frccUngii  in  a.  shallow  wash  on  slope  of  upper  plain  near  Oodnadatta. 

B.  Eremophila  freelingii  in  a  shallow  wash  on  the  edge  of  upper  plain  west  of  Neales  River, 

Oodnadatta. 


A.  Acacia  catnhadgei  in  a  shallow  wash  on  the  slope  eoniieetinj; 

upper  and  lower  plains  west  of  Neales  River,  Oodnadatta. 

B.  Shoot-tips   with  leaves,   Eremophila  freelingii,   from   upper 

plain  west  of  Neales  River,  Oodnadatta. 

C.  Shcot-tips  with  leaves,   Eremophila  latrohei,   from   a   wash 

connecting  upper   and    lower    j^lains  west  of    Neales 
River,  Oodnadata. 


A.  Acacia  tetragonophylla,  near  west  base  of  sandhills  cast  of  Oodnadutta. 

B.  Acacia  linophylla  on  sandhills  east  of  Oodnadatta. 

C.  Short  channel,  Neales  River,  with  Eucalyptus  rostraia  and  Acacia  slenophylla,  small 

shrubs,  on  the  banks,  Oodnadatta. 


fUOfERTT  iMAVf 


A.  Phyllodia  of  Acacia  linophyUa  from  sandhills  near  Oodnadatta. 

B.  Eremophila  neglectg  near  base  of  sandhills  oast  of  Oodnadatta. 

C.  Neales  River  bottoms  from  the  lower  plain,  Oodnadatta. 


A.  Shoot-tips  and  phyllodia  of  Acacia  tdragonophylla,  left,  and  A.  cambadgei,  right,  from  Neales 

River,  Oodnadatta.  ,      , 

B.  Leaves  and  phyllodia  of  Acacia  stenophylla  from  Neales  River,  Oodnadatta. 


^% 


A.  Prominent  development  of    horizontal   roots   in  Acacta  c<unh<ul,jn, 

Xeales  River,  Oodnadatta.  a      i    i  • 

B.  Vegetative    reproduction    in  Acacia    slenophyUa   from    flood-plam, 

Neales  River,  Oodnadatta. 

C.  Kochia  sedifolia  on  low  slope  above  Copley  Plain  on  \uilnamutana 

road,  Copley. 


A.  Zygophyllum  fruticosum  at  edge  of  Copley  Plain  by  Table  Mountain.     The  trees 

in  the  background  are  Casuarinalepidophlota,  Copley.  ■    ■    ,u 

B.  Nitraria  schcEberi  hillock  colonies  on  Copley  Plain.    Table  Mountain  is  in  the 

C.  Detaih)Te%°o"?o?onv  of  Niiraria  schcBhen,  showing  horizontal  prostrate  branches 

by  which  the  hillock  colony  is  extended,  Copley. 


A.  Shoot-tip  of  Eremophila  freelingii  from  low  hills  on  .Mriniit  Srilc-;  loail,  Copley. 

B.  Eremophila  oppositifoUa,  showing  leaves  and  flowers  from  rounded  low  hills  on  Mount  Series  road, 

Copley. 

C.  Pholidia  scoparia,  "broom,"  from  low  hills  on  Mount  Series  road  east  of  Copley. 


■'"^' 


A.  Cassia  sturtii,    constituting   a   mono-spceitic   community   on    Mount 

Series  road,  Copley. 
R.  Mono-specific  community  of  Eremophila  freelingii  in  low  hills  along 

Blount  Series  road,  Copley. 
C.  Mono-specific  community  of  Pholidia  scoparia  in  low  hills  on  Mount 

Series  road,  Copley. 


A.  Hakea  leucoptera  on  southern  slope  of  Table  Mountain,  Copley. 

B.  Casuarina  lepidophloia,  or  "oak,"  at  south  base  of  Table  Mountain,  Copley. 

C.  Community  of  Zygophyllum  fruticosum  near  Mount  of  Light,  Copley. 


A.  Petalodylis  labicheoides  from  south  base  of  Table  Mountain,  Copley. 

B.  Casuarina  lepidophloia,  Copley. 

C.  Petalostylis  labicheoides  at  south  base  of  Table  Mountain,  Copley. 

D.  Shoot  habit  of  Hahea  leucoplera,  with  fruit,  from  Table  Mountain,  Copley. 


A.  Melaleuca  glomerata,  the  "white"  tea-tree,  on  a  small  branch  of  Leigh's  Creek. 

Mount  Series  road,  Copley. 

B.  Melaleuca  parviflora,  the  "black"  tea-tree,  near  Myrtle  Springs  road,  Copley. 

C.  Eucalyptus  rostrata,  the  red  gum,  on  Leigh's  Creek,  Copley. 


A.  Ercmnphila  nUcnnfolia  at  side  of  small  wash  near  Mount  of  Light,  Copley. 

B.  Eremophila  longifolia  on  edge  of  Copley  Plain  near  Leigh's  Creek,  Copley. 


A.  Shoot-tip  showing  leaves  and  fruits  of  Melaleuca  -parviflora,  or  "bhick"  tea-tree, 

from  Myrtle  Springs  road,  Copley. 

B.  Tip  of  shoot  of  Eremophila  alternifolia  with  flowers  and  leaves,  Copley. 

C.  Leafy  shoot  of  Acacia  varians  from  a  wash  east  of  Copley. 

D.  Melaleuca  glomerata,  or  "white"  tea-tree,  from  Leigh's  Creek,  Copley. 


A.  Eremophila  longifolia,  Copley.  „    ,•  j   ■   a 

B.  Branch  of  Acacia  tetragonophylla  with  short  spinose  pliyllodia  and  inHorescence 

buds,  Coplev.  <•/-.! 

C.  Acacia  telragonoplvjUa  in  low  lull^^  on  Mount  Series  road,  east  ot  Copley. 


A.  Leafy  shoot-tips  with  fruit  of  Fusanus  spicatus,  the  "fiuandanp,"  and  F.  arumittatHS,  the 

native  "peach,"'  Mount  Deception  Range,  Copley. 

B.  Myoporum  platycarpum  from  low  hills  on  Mount  Series  road.  Copley. 

C.  Shoot-tip  with  leaves  and  fruit  of  Loranlhus  exocarpi  and  leafy  branch  of  host,  Acacia 

sentis,  Copley. 

D.  Loranthiis  exocarpi,  at  right,  and  Ercmophila  hrownii,  host,  Copley. 


A.  Loranthus  quandang,  with  oval  leaves,  and  the  narroNV-leaved  form  of  Acncia  aneura,  the 

"mulga,"  its  host.     From  Mount  Series  road,  east  of  Copley. 

B.  Loranthus  linearifulius  on  Acacia  tetragonophylla.     The  host  is  shown  with  c-haracteristic 

spine-like  phyllodia.     Coplev. 

C.  Loranthus  excarpi,  with  leaves  and  fruit  and  shoot-tip  of  its  host,  Myoporum  platycarpum. 

Copley. 


A.  Acacia  ancura,  the  mulga,  at  Ooldea. 

B.  Eucalyptus  oleosa  by  a  wash  at  the  eastern  base  of  Mount  Deception  Ranf^e.     The  prominent 

stem  base  and  enlarged  crown  of  the  taproot,  both  characteristic  of  the  "raallee,"  are 
shown.     Copley. 


A.  Detail  of  branch  of  Acacia  collelioides,  showinji  spine-like  phj-llcdia.    Ooldea. 

B.  Narrow  "leaf"  form  of  Acacia  aneura,  the  mulga,  at  Ooldea.     Young  fruit  is  shown  on  one  branch 

C.  Broad  "leaf"  form  of  Acacia  aneura,  the  mulga,  at  Ooldea. 


A.  Eucalyptus   p.nfonnis  at  Ooldea.     \-ar;ous  sp..-u-.  ul    A,ana  ai.a   tl...   nKdhrh ucaiyplus 

'inrrns.ah,  \  ar.  f/(/wosa,  make  up  the  surrounding  woody  vegetation.      J  he  floor  is  bare. 

B.  Eucalyptu,  lujcoxijlon  var.  macrocarpa,  middle  ground,  and  E.  incrassata  var.  dumom,  on  the 

hillside  bcj-ond,  near  Ooldea. 


A.  Fruits  of  Eucalyptus  pyrifonnis  from  Ooldea.  The  fruits  arc  about  5  cm.   in 

diameter.  ,     /-,  i  i      o     i 

B.  Leptospermum  Uvviqaium  var.  minus,  in  flower,  from  the  Ooldea  boak. 

C.  The  shrubby  Eucalyptus  leucoxylon  var.  macrocarpa,  in  flower,  from  btation  4U», 

near  Ooldea. 


A.  Pholidia  santalina  from  mallee  community  on  low  ridge  west  of  Quorn. 

B.  CaUistemon  teretifoUus  from  ridge  on  Mount  Arden  road,  Quorn. 

C.  Aphyllous  Acacia  conlinua  from  low  hills  on  the  Pichi  Richi  road,  west  of  Quorn. 

D.  Tip  of  branch  of  Acacia  calaniifolia,  in  fruit,  showing  the  linear  phyllodia.     From  open 

Casuarina  forest  on  the  Melrose  road,  east  of  Quorn. 


A.  Gramllea  stenobolrya  shoot,  showing  leaves  and  fruits,  from  Station  40S,  near  Ooldea. 

B.  Leaf  habit  of  Eremophila  rotundifolia,  Tarcoola. 

C.  Tips  of  a  branch  of  Acacia  rigens,  with  phyllodia. 

D.  A  fruiting  branch  of  Acacia  larculiensis,  showing  characteristic  pl)\-I!odia.     From 

type  habitat,  Tarcoola. 


^     .1"'-    '     :    "\,  the  "myall,"  with  varioashalophyte'^,<  in  pLun  iimi;  I,  ,,ri'.irc.„;la. 

B.  Tliicket  of  luallee,  Eucalyptus  oleosa,  on  sloping  saUbash  plain,  foolhilLs  of  the 

Flinders,  east  of  Port  Augusta,  near  Saltia. 

C.  "Beef  wood,"  Gmvillea  slenoholrya,  on  the  crest  of  sandhill  by  Station  408,  near 

Ooldea. 


A.  Forest  of  Eucalyptus  roslrata  on  8altia  Creek,  east  of  Port  Augusta. 

B.  Pine  community,  Callitris  robusta,  at  Warren's  Gorge,  near  Quorn. 

C.  View  in  mallee  scrub,  about  2  miles  north  of  Quorn.     Eucalyptus  odoruta  and 

E.  oleosa  in  background.     Bunches  of  Triodia  irritans  in  foreground. 


A.  Branches  of  Acacia  sublanata,  showing  small  and  rigid  phyllodia.     Quorn. 

B.  Eutaxia  empetrifolia,  showing  the  small  flowers  and  linear  short  leaves.     Quorn. 

C.  Branches  of  Acacia  ■pycnanlha,  the  "golden  wattle,"  showing  the  character  of  the  large 

phyllodia.     Quorn. 


A.  View  about  2  miles  we-'  -      ;  ,  iioni  a  grassy  ridpe  and  lookintr  upon  a 

ridge  which  is  covcnHl  with  iiiallce.     In  the  intervening  valley  are  a  few 
specimens  of  Eucalyptus  Icucoxijlon  var.  pauperita. 

B.  Hakca  leucoptera  on  the  edge  of  the  mallee  scrub,  a})0ut  2  miles  north  of  Qiiorn. 

Small  shoots  which  spring  from  superficial  roots  of  the  larger  plants  are 
in  the  foreground.  * 

C.  Western  slope  of  ridge  along  Mount  Arden  roa<l,  Quorn,  with  Triodia  irritom  and 

Trichiniuni,  dominant  grasses.     Dead  fruiting  stalks  of  Xanthorrhcea  serni- 
plana  show  in  the  foreground;  mallee,  Eucalyptus  sp.,  in  the  background. 


A.  Bossicea  walkeri  on  summit  of  a  sandhill  l)y  Station  lOS.  near  OoKlca. 

B.  Hakea  multilineala  on  the  crest  of  a  sandhill  by  Station  4()S,  near  Ooldea,  with  ^«ca- 

hjplus  incrassala  var.  durnosa,  a  mallee,  in  the  flats  below.     Bunches  of  spinifex, 
Triodia  irrilaus,  are  to  be  seen  between  the  mallee. 

C.  Branch  with  withered  flower-spike  and  leaves  of  Hakea   muUaineata,  from  Station 

408,  near  Ooldea.  . 

D.  Melaleuca  uncinata  in  fruit,  from  the  sandhills  by  Station  408,  near  Ooldea. 


f 

p^. 

v 

m 

■r 

f^ 

' 

' 

,  ..'-^^s 

w 

Jf^.'. 

V,, 

r       .  T 

,,:..;i.rf 

^. 

A.  Community  of  Acacia  pijcnantha,  tli(>  fioldcn  wattlf.  by  a  streamway  on 

the  Mount  Brown  road,  Quorn. 

B.  Large  specimen  of  EucalypKis  leucoxylon  var.  ;;o»pcr^/al)3'fl  wash  on  the 

Mount  Arden  road,  Quorn.      A  comparison  with  the  automobile 
will  give  an  idea  of  its  size. 
C    Vegetative  reproduction  in  Hakca  leucoptcra.     A  young  shoot,  removed 
from  the  soil,  is  shown  taking  its  origin  from  a  horizontal  root. 
Quorn. 


A.  Exposure  of  roots  of  malloe,  Eucalyptus  sp.,  l>y  u  narrow  wa-sh,  showinK  the  iil)un(lancc  of 

superficial  roots.     Along  the  Mount  Arden  road,  Quorn. 

B.  Root  exposure  of  Eucalyptus  leucoxylon  var.  pauperita  by  erosion  of  the  bank  of  stream  above 

Warren's  Gorge.     The  roots  were  washed   out  for  a  distance  exceeding  16  meters. 
Quorn. 


If'^ 


c— 


^^^fSi^ 


^■ 


Ji- 


A.  Scattered  groups  of  Melaleuca  parriflora,  in  the  mallee  scrub  near  Blanchtown. 

B.  Flood  plain  of  the  iNIurrayRiver.shovving  open  forest  of  Eucalyptus  rostrata  partly  sul. 

Blanchtown. 

C.  View  in  mallee,  Eucalyptus  sp.,  scrub  on  Murray  flats  near  Blanchtown. 


